Nasreen Haque asked:


Fujitsu desktop computers are a great alternative to the more well-known desktop brands. There are several unique features that make the Fujitsu desktop computers stand out from other desktop computers. If you are looking for a computer that has a lot of versatility and many other great features then the Fujitsu may be right for you. The Fujitsu computer is similarly priced to other computer models, but since it contains many features and benefits Fujitsu computers stand out as a clear choice.

Fujitsu computers come with a large amount of processing power. Most of them have an Intel Core Duo processing unit, which makes the processing power of the computers faster than any computer that just has a single processing unit. Duo processing means processes take half as long. The processing unit of the Fujitsu is also environmentally friendly.

The processing unit is not the only part of Fujitsu desktop computers that are environmentally friendly. All Fujitsu computers comply with the European Union’s Restriction of Hazardous Substances procedures. Fujitsu also chooses products and materials that are safer for human use as well. This makes Fujitsu computers some of the most environmentally sound among the many brands any available in the market today.

Another great feature of Fujitsu computers is their ability to expand with additional hardware options. Fujitsu computers come with multiple PCI and PCI express slots which make it easy to install extra memory, network options, and other hardware needs. The multiple expansion slots make Fujitsu one of the most easily modified computers. Modification capabilities are becoming rarer these days, so a computer that still offers customization is a major plus.

Another great feature of Fujitsu computers is the graphics capabilities. With many computers the graphics card that comes with the computer is too small to run many games or programs. The graphics card that comes with a Fujitsu computer is capable of running almost any game out in the market today. Fujitsu computers also come fully equipped with the Windows Vista operating system.

A Fujitsu computer also comes with many external card reader slots and USB ports. The inclusion of so many different types of card readers makes it easy for anyone to upload their pictures or other information onto the Fujitsu computer. Fujitsu computers come with a card reader that is compatible with almost any memory device out there.

The last great benefit of a Fujitsu computer is the design of the CPU. The computer is designed to be taken apart and put back together quite easily. This makes it easy not only for users to upgrade the computer, but it also means that when the computer has to be taken in for repairs that they are able to be completed quickly and efficiently. The use of the easy-access CPU style is one of the biggest things that stick out about Fujitsu computers.

If you have never considered purchasing a Fujitsu computer, then consider looking into it for your next computer purchase. With all the features and benefits offered by Fujitsu, you will not be disappointed.



WALTER

Joe Uantu asked:


Hurricanes cause billions of dollars in damage each year, including damage to computers. Unfortunately, computers can be much harder to replace if lost than other electronics because of the data contained on their hard drives and time spent tweaking and overclocking them. Being a Katrina evacuee and survivor myself, I know how important a computer can be after a natural disaster. With hurricane season looming in the days ahead, I decided to write a guide to help people protect their computers and data during a natural disaster.

Part I: Backing Up Data And Things to Have

Hurricane season or not, you should always be backing up your data. Whether you plan on riding out the storm (a bad idea) or evacuating to another location, you should have a backup of your computer data either on an external hard drive or optical media such as CD-Rs or a DVD. Be sure to keep your data in a very safe place, such as a water proof safe. Never leave your backup by your computer.

Next, you should have the following things to make life after the storm easier:



Phone numbers for insurance, computer or computer parts companies, and phone numbers for all local ISPs (including dial-up and satellite). Having your insurance phone number and phone numbers for your computer company will help get your computer replaced faster if it is damaged. I can’t stress enough how important it is for you to have phone numbers and even access disks for all of your local ISPs! After Katrina, the Internet was the only way many people could contact the outside world. As fate would have it, my broadband was down for 3 weeks and none of the other broadband ISPs would except new orders due to the storm, leaving me with my old friend Dial Up, whom I thought I had buried 8 years ago. Your best bet is to use a satellite ISP as they have no equipment that can be destroyed by a hurricane and cause an outage.



Back ups of all your file, have all application and game discs, CD keys, drivers, and operating system discs on hand.



Photos of your computer as well as proof of what parts are inside.



In the event your quad SLI rig is destroyed, you don’t want your insurance company to replace it with something of a significantly lesser value, do you? It’s very easy for people to claim “I had this, this, and this and it all cost me $3000 last month.” after their 3 year old Athlon XP rig is destroyed. As a result, your insurance company may be hesitant to replace your expensive computer parts unless you can prove you own them. Also know to what extent your insurance (including flood insurance) will replace damaged property. While some policies will cover the replacement cost of damaged property, some may only cover part of the damage cost. Also know what your deductible is.

Blog or Social Networking Profile

Social networking sites such as myspace were great after Katrina. Friends could find out where other friends had evacuated to simply by reading each others’ myspaces.

Generator and Gas

A generator can power many things, including home computers! Check with your local generator supplier about any local laws about generators, how to safely and properly set one up, and how well they will work with computers. Because generators provide unstable power, a battery backup UPS and a surge protector are a must. Do not count on gas to power your generator being available in the aftermath of the storm. It’s best to have a good supply of gas as well as a few empty gas containers on hand.

Part II: Evacuating with Your PC

Like any family members or pets you may have, your PC isn’t something to leave behind if you can avoid it. While your first priority should be getting out alive, you should consider bringing your PC with you if you can room in your car. You can’t count on your destination to have good computers, high speed Internet, or any entertaining activities for that matter. Being in another place during a hurricane is stressful. Between watching your home town being walloped on CNN and The Weather Channel, the people around you as well as yourself will be tense and worried. Having a nice computer to browse the web with and play Battlefield 2 is a sure entertainer. In fact, the Internet was the only place where I could get information about my very neighborhood after the storm! Local newspaper message boards were packed with evacuees from all over my area and had plenty of information about damage to share.

Even if you can’t bring your PC, at the very least bring your hard drive with you! If your home is looted in the aftermath of the storm, the last thing you want is your personal data in someone else’s hands. Be sure your hard drive is in an anti-static bag to avoid needless damage to it.

If taking a long road trip, you should probably place some sort of padding or foaming (even a blanket will work) around your computer or hard drive to protect it from the vibrations of the car. Don’t bring your monitor unless you have an LCD and there’s room for it.

Part III: Leaving Your PC at Home

If you don’t have room for your PC in your car, don’t plan on staying with it during the storm. There are several safeguards you can take to prevent unnecessary damage to your computer:



Cover any open parts of your computer case (such as fans and vents) with tape. Don’t use duct tape unless you want to risk taking paint off your case or a sticky mess.



Cover your computer with as many trash bags as you need. At least 2 trash bags per computer are recommended.



Consider how high your home is above sea level, the risk of flooding, and other factors. If you know your home could flood, you should put your computer on the second floor. But if you know your roof is weak and could easily blow off, don’t put it on the second floor! Find an enclosed space with no windows (such as a closet) as close to the center of your home as possible. If your computer case has a side window, make sure it’s facing towards the ground or against a wall. If you can, place other objects around your computer to offer it additonal protection from blowing rain and flying debris.



Part IV: When the Worst Happens

In the event your PC becomes damaged during the storm, don’t fret. If the damage is from a fallen tree or a piece of flying debri, there is nothing you can do. If your computer becomes flooded, however, there are steps you can take to recover it. Below is a basic guide on how to recover a flooded computer.



Do not turn on the computer! Make sure it is unplugged! While you may be anxious to see if your computer can run, don’t do it if you know it’s been exposed to water. You’ll just end up causing more damage if you do. Remember to keep your computer unplugged.



Remove components that work. If you can see a water line in your computer, take out all the components above it and put them in a safe place.



Let your computer dry. Let your computer dry for a week or so. One drop of water in a running computer could mean disaster.



Remove the CMOS battery and other parts.



Use a solution of 90% alcohol or more to wash the various components of your computer, including connectors. If necessary, use a paint brush to remove stubbon crud.



Let your computer dry completely.



If the above doesn’t work or you have data you can’t risk losing on your hard drive, consider professional computer recovery. Do not plan on salvaging the power supply, CMOS battery, the hard drive, optical drives, or any fans if they have been flooded. Also remember to take pictures of any damage to your computer before you attempt to fix it for insurance purposes.

Hopefully this guide will help people save their computers from hurricane related damage. A computer is a very useful tool that should be part of any good disaster supply kit. Trust me when I say it’s an important thing to have around. However, remember a computer is only a material possession. Like all material objects, they can be replaced. Human and animal life, however, cannot. Use good judgement when deciding whether or not to take your computer with you and while repairing it if it damaged.

Disclaimer: In no way is the author responsible for any actions you may take to save your computer from a hurricane or fix it after flooding. Any actions you choose regarding hurricanes and computers are taken at your own risk. For the sake of all, please use common sense during any natural disaster.



COLIN

Dianne Rein asked:


A scuba diving computer can be a divers best friend. It will allow you to stay down longer than if you were diving off of tables. There are many types and/or styles of dive computers you can choose from. Which one is best is really personal preference and is suited to the way you dive. The following are some of the choices you will have when purchasing your dive computer.

Console Dive Computer

A console dive computer is attached to the rest of the equipment via a hose. The console dive computers typically come with a pressure gauge. The readouts are typically larger than on a wrist dive computer so they can also be easier on the eyes.

There are also options for a scuba dive computer to be mounted on your hose (this is the type we currently use) or clip onto your BC. Choose whichever is more comfortable for you and fits into your price range.

Wrist Dive Computer

The wrist dive computer is very popular. These types of computers look like large watches and are worn on the wrist. They will tell you all you need to know at a glance. Some wrist dive computers are also able to be mounted in a console.

Sometimes the faces may be a bit small for all the information the computer can display, so make sure you will be able to read it underwater.

Unless they are air integrated and wireless (see below) wrist dive computers usually do not come with a pressure gauge. One small disadvantage here is that these can be pretty easy to misplace/lose.

Air Integrated Dive Computer

Air integrated dive computers are becoming more commonplace. An air integrated computer measures the tank pressure and then calculates how much more time you have left at the current rate of air consumpetion. The air integrated dive computer will tell you how much time you can spend at any exertion level.

An air integrated computer replaces the need for a submersible pressure gauge (SPG). One downside of an air integrated computer is that if it fails, you lose information on how much air you have left in your tank. Dive over.

Nitrox Dive Computer

With nitrox diving becoming more and more common, so are computers that are nitrox compatible. Even if you aren’t diving with nitrox now, if you are even thinking of diving with nitrox in the future, it is probably worth it to purchase a nitrox dive computer. This will save you the expense of buying a whole new computer in the future. However, if don’t think you will ever dive with nitrox, then there is no reason to pay for this feature. A standard air computer is probably $100+ less than its nitrox counterpart.

Hoseless Dive Computer

The hoseless dive computer consists of the receiver (typically worn on the wrist or mounted on the BC) and a transmitor. The transmitor attaches to the high pressure port of the regulator first stage and then sends your air information, wirelessly, to the receiver. The receiver looks the same as normal dive computers.

This setup cuts down on the number of hoses you need. There are now even hoseless dive computers that can accept signal from multiple transmitors - so you can even keep an eye on your buddies air consumption. Of course, this capability is really for the more advanced technical divers who may use different tanks on one dive. And, of course, we are talking some pretty high price tags here.

So just think about how you dive and what capabilities you need. The right dive computer for one person can be completely wrong for another person. Choose one that you are comfortable with and one that is right for you wallet.



ELI

Rick R asked:


I had two computers both connected to a wireless router. Yesterday I connected a third computer to the network and, although the connection goes through for this new computer, one of the original computers now says “Limited or no connectivity” and cannot connect to the Internet. Is it possible that the new computer is using up too much bandwidth and is therefore preventing the other computer from accessing the Internet?

ELTON

eloro_calion asked:


I only have one processor slot on my motherboard, but I have another computer that is basically stripped of everything useful (DVD drives, ram, etc, etc). All that is left is the hard drive, motherboard and processor, power and the fans. I want to use this computer to share workload with my main desktop. I know I can’t connect the motherboards or processors (Pentium 4s), but I know it is possible to connect the computers somehow.

BRADFORD

CHAYAN SUR asked:


In 1983, Fred Cohen coined the term “computer virus”, postulating a virus was "a program that can ‘infect’ other programs by modifying them to include a possibly evolved copy of itself.” The term virus is actually an acronym for Vital Information Resources Under Seize. Mr. Cohen expanded his definition a year later in his 1984 paper, “A Computer Virus”, noting that “a virus can spread throughout a computer system or network using the authorizations of every user using it to infect their programs. Every program that gets infected may also act as a virus and thus the infection grows.” Computer viruses, as we know them now, originated in 1986 with the creation of Brain - the first virus for personal computers. Two brothers wrote it (Basid and Farooq Alvi who ran a small software house in Lahore, Pakistan) and started the race between viruses and anti-virus programs which still goes on today.

Using the above explanation, it can be said that viruses infect program files. However, viruses can also infect certain types of data files, specifically those types of data files that support executable content, for example, files created in Microsoft Office programs that rely on macros.

Compounding the definition difficulty, viruses also exist that demonstrate a similar ability to infect data files that don’t typically support executable content - for example, Adobe PDF files, widely used for document sharing, and .JPG image files. However, in both cases, the respective virus has a dependency on an outside executable and thus neither virus can be considered more than a simple ‘proof of concept’. In other cases, the data files themselves may not be infectable, but can allow for the introduction of viral code. Specifically, vulnerabilities in certain products can allow data files to be manipulated in such a way that it will cause the host program to become unstable, after which malicious code can be introduced to the system. These examples are given simply to note that viruses no longer relegate themselves to simply infecting program files, as was the case when Mr. Cohen first defined the term. Thus, to simplify and modernize, it can be safely stated that a virus infects other files, whether program or data.

Computer viruses are called viruses because they share some of the traits of biological viruses. A computer virus passes from computer to computer like a biological virus passes from person to person.

There are similarities at a deeper level, as well. A biological virus is not a living thing. A virus is a fragment of DNA inside a protective jacket. Unlike a cell, a virus has no way to do anything or to reproduce by itself — it is not alive. Instead, a biological virus must inject its DNA into a cell. The viral DNA then uses the cell’s existing machinery to reproduce itself. In some cases, the cell fills with new viral particles until it bursts, releasing the virus. In other cases, the new virus particles bud off the cell one at a time, and the cell remains alive.

A computer virus shares some of these traits. A computer virus must piggyback on top of some other program or document in order to get executed. Once it is running, it is then able to infect other programs or documents. Obviously, the analogy between computer and biological viruses stretches things a bit, but there are enough similarities that the name sticks.

A computer virus is a program that replicates. To do so, it needs to attach itself to other program files (for example, .exe, .com, .dll) and execute whenever the host program executes. Beyond simple replication, a virus almost always seeks to fulfill another purpose: to cause damage.

Called the damage routine, or payload, the destructive portion of a virus can range from overwriting critical information kept on the hard disk’s partition table to scrambling the numbers in the spreadsheets to just taunting the user with sounds, pictures, or obnoxious effects.

It’s worth bearing in mind, however, that even without a ”damage routine”, if viruses are allowed to run unabated then it will continue to propagate–consuming system memory, disk space, slowing network traffic and generally degrading performance. Besides, virus code is often buggy and can also be the source of mysterious system problems that take weeks to understand. So, whether a virus is harmful or not, its presence on the system can lead to instability and should not be tolerated.

Some viruses, in conjunction with "logic bombs," do not make their presence known for months. Instead of causing damage right away, these viruses do nothing but replicate–until the preordained trigger day or event when they unleash their damage routines on the host system or across a network.

Impact of Viruses on Computer Systems

Virus can be reprogrammed to do many kinds of harm including the following.

1.Copy themselves to other programs or areas of a disk.

2.Replicate as rapidly and frequently as possible, filling up the infected system’s disk and memory rendering the systems useless.

3.Display information on the screen.

4.Modify, corrupt or destroy selected files.

5.Erase the contents of entire disks.

6.Lie dormant for a specified time or until a given condition is met, and then become active.

7.Open a back door to the infected system that allows someone else to access and even control of the system through a network or internet connection.

8.Some viruses can crash the system by causing some programs (typically Windows) to behave oddly.

How viruses spread from one system to another?

The most likely virus entry points are email, Internet and network connections, floppy disk drives, and modems or other serial or parallel port connections. In today’s increasingly interconnected workplace (Internet, intranet, shared drives, removable drives, and email), virus outbreaks now can spread faster and wider than ever before.

The following are some common ways for a virus to enter the users’ computer system:

•Email attachments

•Malicious scripts in web pages or HTML email

•FTP traffic from the Internet (file downloads)

•Shared network files & network traffic in general

•Demonstration software

•Pirated software

•Shrink-wrapped, production programs (rare)

•Computer labs

•Electronic bulletin boards (BBS)

•Diskette swapping (using other people’s diskettes for carrying data and programs back and forth)

High risk files

The most dangerous files types are:

.EXE, .COM, .XLS, .DOC, .MDB

Because they don’t need any special conversion to infect a computer — all they’ve got to do is run and consequently the virus spreads. It has been estimated that 99% of all viruses are written for these file formats.

A list of possible virus carriers includes:

EXE - (Executable file)

SYS - (Executable file)

COM - (Executable file)

DOC - (Microsoft Word)

XLS - (Microsoft Excel)

MDB - (Microsoft Access)

ZIP - (Compressed file, common in the USA)

ARJ - (Compressed file, common in the USA)

DRV - (Device driver)

BIN - (Common boot sector image file)

SCR - (Microsoft screen saver)

Common Symptoms Of Virus Infection

?Computer does not boot.

?Computer hard drive space is reduced.

?Applications will not load.

?An application takes longer to load than normal time period.

?Hard dive activity increases especially when nothing is being done on the computer.

?An anti virus software message appears.

?The number of hard drive bad sectors steadily increases.

?Unusual graphics or messages appear on the screen

?Files are missing (deleted)

?A message appears that hard drive cannot be detected or recognized.

?Strange sounds come from the computer.

?Some viruses take control of the keyboard and occasionally substitute a neighboring key for the one actually pressed. Another virus "swallows" key presses so that nothing appears on the screen.

?Also interesting are system time effects. Clocks going backwards are especially frightening for workers who cannot wait to go home. More seriously though, this type of virus can cause chaos for programs which depend on the system time or date.

?Some viruses can cost the user dearly by dialing out on his modem. We do not know of one which dials premium telephone numbers but no doubt we shall see one soon. One particularly malicious virus dials 911 (the emergency number in the USA) and takes up the valuable time of the emergency services.

Categories of viruses

Depending on the source of information different types of viruses may be categorized in the following ways:

PDA VIRUSES

The increasing power of PDAs has spawned a new breed of viruses. Maliciously creative programmers have leveraged the PDA’s ability to communicate with other devices and run programs, to cause digital mayhem.

The blissfully safe world where users of these devices could synchronize and download with impunity came to an end in August 2000 with the discovery of the virus Palm Liberty. Since then, many more viruses have been discovered.

Though not yet as harmful as their PC-based cousins, these viruses still pose a threat to unsuspecting users. Their effects vary from the harmless flashing of an unwanted message or an increase in power consumption, to the deletion of all installed programs. But the threat is growing, and the destructiveness of these viruses is expected to parallel the development of the devices they attack.

MULTIPARTITE VIRUSES

A virus that combines two or more different infection methods is called a multipartite virus. This type of virus can infect both files and boot sector of a disk. Multi-partite viruses share some of the characteristics of boot sector viruses and file viruses: They can infect .com files, .exe files, and the boot sector of the computer’s hard drive. On a computer booted up with an infected diskette, the typical multi-partite virus will first make itself resident in memory then infect the boot sector of the hard drive. From there, the virus may infect a PC’s entire environment. Not many forms of this virus class actually exist. However, they do account for a disproportionately large percentage of all infections. Tequila and Anticad are the examples of multipartite viruses.

BOMBS

The two most prevalent types of bombs are time bombs and logic bombs. A time bomb hides on the victim’s disk and waits until a specific date before running. A logic bomb may be activated by a date, a change to a file, or a particular action taken by a user or a program. Bombs are treated as viruses because they can cause damage or disruption to a system.

BOOT SECTOR VIRUSES

Until the mid-1990s, boot sector viruses were the most prevalent virus type, spreading primarily in the 16-bit DOS world via floppy disk. Boot sector viruses infect the boot sector on a floppy disk and spread to a user’s hard disk, and can also infect the master boot record (MBR) on a user’s hard drive. Once the MBR or boot sector on the hard drive is infected, the virus attempts to infect the boot sector of every floppy disk that is inserted into the computer and accessed. Examples of boot sector viruses are Michelangelo, Satria and Keydrop.

Boot sector viruses work like this: Let us assume that the user received a diskette with an infected boot sector. The user copied data from it but forgot to remove it from drive A:. When he started the computer next time the boot process will execute the infected boot sector program from the diskette. The virus will load first and infect the hard disk. Note that this can be prevented by changing the boot sequence in CMOS (Let C: drive boot before A:). By hiding on the first sector of a disk, the virus is loaded into memory before the system files are loaded. This allows it to gain complete control of DOS interrupts and in the process replaces the original contents of the MBR or DOS boot sector with their own contents and move the original boot sector data to another area on the disk. Because the virus has infected a system area of the hard disk it will be loaded into memory each time the computer is started. It will first take control of the lowest level disk system services before executing the original boot sector code which it has stored in another part of the hard disk. The computer seems to behave exactly as it should. Nobody will notice the extra few fractions of a second added to the boot sequence.

During normal operation the virus will happily stay in memory. Thanks to the fact that it has control of the disk services it can easily monitor requests for disk access - including diskettes. As soon as it gets a request for access to a diskette it will determine that there is a diskette in the floppy drive. It will then examine its boot sector to see if it has already been infected. If it finds the diskette clean it will replace the boot sector with its own code. From this moment the diskette will be a "carrier" and become a medium for infections on other PC’s.

The virus will also monitor special disk requests for access to the boot sector. The boot sector contains its own code, and a request to read it could be from an anti-virus program checking for virus presence. The virus will not allow the boot sector to be read and will redirect all requests to the place on the hard disk where it has backed up the original contents. In this way nothing unusual is detected. Such methods are called stealth techniques and their main goal is to mask the presence of the virus. Not all boot viruses use stealth but those which do are common.

Boot viruses also infect the non-file (system) areas of hard and floppy disks. These areas offer an efficient way for a virus to spread from one computer to another. Boot viruses have achieved a higher degree of success than program viruses in infecting their targets and spreading.

Boot virus can infect DOS, Windows 3.x, Windows 95/98, Windows NT, and even Novell Netware systems. This is because they exploit inherent features of the computer (rather than the operating system) to spread and activate.

Cleaning up a boot sector virus can be performed by booting the machine from an uninfected floppy system disk rather than from the hard drive, or by finding the original boot sector and replacing it in the correct location on the disk.

CLUSTER VIRUSES

This type of virus makes changes to a disks file system. If any program is run from the infected disk, the program causes the virus to run as well. This technique creates the illusion that the virus has infected every program on the disk.

E-MAIL VIRUSES

These types of viruses can be transmitted via e-mail messages sent across private networks or the internet. Some e-mail viruses are transmitted as an infected attachment- a document file or program that is attached to the message. This type of virus is run when the victim opens the file that is attached to the message. Other types of email viruses reside within the body of the message itself. To store a virus, the message must be encoded in html format. Once launched many e-mail viruses attempt to spread by sending messages to everyone in the victim’s address book; each of those contains a copy of the virus.

The latest thing in the world of computer viruses is the e-mail virus called Melissa virus which surfaced in March 1999. Melissa spread in Microsoft Word documents sent via e-mail, and it worked like this:

Someone created the virus as a Word document uploaded to an Internet newsgroup. Anyone who downloaded the document and opened it would trigger the virus. The virus would then send the document (and therefore itself) in an e-mail message to the first 50 people in the person’s address book. The e-mail message contained a friendly note that included the person’s name, so the recipient would open the document thinking it was harmless. The virus would then create 50 new messages from the recipient’s machine. As a result, the Melissa virus was the fastest-spreading virus ever seen and it forced a number of large companies to shut down their e-mail systems at that time.

The ILOVEYOU virus, which appeared on May 4, 2000, was even simpler. It contained a piece of code as an attachment. People who double clicked on the attachment allowed the code to execute. The code sent copies of itself to everyone in the victim’s address book and then started corrupting files on the victim’s machine. This is as simple as a virus can get. It is really more of a Trojan horse distributed by e-mail than it is a virus.

The Melissa virus took advantage of the programming language built into Microsoft Word called VBA, or Visual Basic for Applications. It is a complete programming language and it can be programmed to do things like modify files and send e-mail messages. It also has a useful but dangerous auto-execute feature. A programmer can insert a program into a document that runs instantly whenever the document is opened. This is how the Melissa virus was programmed. Anyone who opened a document infected with Melissa would immediately activate the virus. It would send the 50 e-mails, and then infect a central file called NORMAL.DOT so that any file saved later would also contain the virus! It created a huge mess.

FILE INFECTING VIRUSES

File infectors operate in memory and usually infect executable files with the following extensions: *.COM, *.EXE, *.DRV, *.DLL, *.BIN, *.OVL, *.SYS. They activate every time the infected file is executed by copying themselves into other executable files and can remain in memory long after the virus has activated.

Thousands of different file infecting viruses exist, but similar to boot sector viruses, the vast majority operates in a DOS 16-bit environment. Some, however, have successfully infected the Microsoft Windows, IBM OS/2, and Apple Computer Macintosh environments.

File viruses can be separated further into sub-categories by the way they manipulate their targets:

TSR FILE VIRUSES

A less common type of virus is the terminate-and-stay-resident file virus. As the name suggests these infect files usually these are .com and .exe files. there are however some device driver viruses, some viruses that infect overlay files, and although over 99% of executable programs have the extension .com and .exe, some do not .For a TSR virus to spread some one has to run an infected program. The virus goes memory resident typically looking at each program run thereafter and infects it. Examples of TSR file viruses are Dark Avenger and Green Caterpillar.

OVERWRITING VIRUSES

These viruses infect by overwriting part of their target with their own code but, by doing so, they damage the file. The file will never serve another purpose other than spreading the virus further. Because of this they are usually detected quickly and do not spread easily.

PARASITIC VIRUSES

These viruses attach themselves to executables without substantially changing the contents of the host program. They attach by adding their code to the beginning, end, or even middle of the file and divert program flow so that the virus is executed first. When the virus has finished its job, control is passed on to the host. Execution of the host is a little delayed but this is usually not noticeable.

MACRO VIRUSES

Many older applications had simple macro systems that allowed the user to record a sequence of operations within the application and associate them with a specific keystroke. Later, the user could perform the same sequence of operations by merely hitting the specified key.

Newer applications provide much more complex macro systems. User can write entire macro-programs that run within the word processor or spreadsheet environment and are attached directly onto word processing and spreadsheet files. Unfortunately, this ability also makes it possible to create macro viruses.

Macro viruses currently account for about 80 percent of all viruses, according to the International Computer Security Association (ICSA), and are the fastest growing viruses in computer history. Unlike other virus types, macro viruses aren’t specific to an operating system and spread with ease via email attachments, floppy disks, Web downloads, file transfers, and cooperative applications.

Macro viruses are, however, application-specific. A macro virus is designed to infect a specific type of document file, such as Microsoft word or excel files. They infect macro utilities that accompany such applications as Microsoft Word and Excel, which means a Word macro virus cannot infect an Excel document and vice versa. A macro virus is embedded in a document file and can travel between data files in the application and can eventually infect hundreds of files if undeterred and in the process do various levels of damage to data from corrupting documents to deleting data.

Macro viruses are written in "every man’s programming language" — Visual Basic — and are relatively easy to create. They can infect at different points during a file’s use, for example, when it is opened, saved, closed, or deleted

A typical chronology for macro virus infection begins when an infected document or spreadsheet is loaded. The application also loads any accompanying macros that are attached to the file. If one or more of the macros meet certain criteria, the application will also immediately execute these macros. Macro viruses rely upon this auto-execution capability to gain control of the application’s macro system.

Once the macro virus has been loaded and executed, it waits for the user to edit a new document, and then kicks into action again. It attaches its virus macro programs onto the new document, and then allows the application to save the document normally. In this fashion, the virus spreads to another file and does so in a completely discrete fashion. Users have no idea of the infection. If this new file is later opened on another computer, the virus will once again load, be launched by the application, and find other unsuspecting files to infect.

Finally, as far as a macro virus is concerned, the application serves as the operating system. A single macro virus can spread to any of the platforms on which the application is installed and running. For example, a single macro virus that uses Microsoft Word could conceivably spread to Windows 3.x, Windows 95/98, Window NT, and the Macintosh.

Macro viruses for Word

In the summer of 1995, Microsoft Word 6 was the first product affected with macro virus. The first one (WM/Concept.A) was really only a proof of concept - one of the installed macros (called Payload) contained only this remark:

“That’s enough to prove my point”

Most macro viruses for Word use a feature called ‘automacros’. The basic principle is that some macros with special names are automatically executed when Word starts, opens a file, or closes a file. The macro virus then inserts macros into NORMAL.DOT - a standard template which is loaded every time Word starts.

In Word there are some ways to disable automacros but this isn’t the ultimate solution. Some macro viruses use other methods to take control over the Word environment.

Another method of self-protection may be to set NORMAL.DOT to read only. But this can also be bypassed and, in addition, it prevents the user from customizing the template.

Macro viruses for Excel

Excel has the same opportunities for virus authors as Word. It has automacros and a directory called XLSTART from which templates are automatically loaded.

But Excel does not have just normal VBA macros like Word. In Excel there are so called ‘formulas’ - macros stored in spreadsheet cells. The first macro virus using this technology was XF/Paix.

Macro viruses for other MS Office products:

Writing a macro virus for other Office products is not difficult. There have been already some viruses for Access, and it is expected that there will be macro viruses for Power Point in the near future.

But those macro viruses are not as dangerous as the macro viruses for Word or Excel. Not because of some limitation of these other Office products, but because data files from these products are not so frequently shared.

There is one danger which can be seen in today’s Power Point even without native macro viruses written for this product. Programmers can include in their presentation any number of objects from Excel or Word. And these objects can be infected with macro viruses - if they edit the presentation and open the infected object with its parent application, then the virus can spread further.

But the current situation may change dramatically over the next few years. Microsoft has licensed VBA technology to many firms, so one can expect to see more macro viruses for other products, too.

POLYMORPHIC VIRUSES

This type of virus can change itself each time it is copied, making it difficult to isolate. Most simple viruses attach identical copies of themselves to the files they infect. An anti-virus program can detect the virus’s code (or signature) because it is always the same and quickly ferret out the virus. To avoid such easy detection, polymorphic viruses operate somewhat differently. Unlike the simple virus, when a polymorphic virus infects a program, it scrambles its virus code in the program body. This scrambling means that no two infections look the same, making detection more difficult. These viruses create a new decryption routine each time they infect, so every infected file will have a different sequence of virus code.

STEALTH VIRUSES

Stealth viruses actively seek to conceal themselves from attempts to detect or remove them. They also can conceal changes they make to other files, hiding the damage from the user and the operating system.

Stealth viruses, or Interrupt Interceptors, as they are sometimes called, take control of key DOS-level instructions by intercepting the interrupt table, which is located at the beginning of memory. This gives the virus the ability to do two important things: 1) gain control of the system by re-directing the interrupt calls, and 2) hide itself to prevent detection. They use techniques such as intercepting disk reads to provide an uninfected copy of the original item in place of the infected copy (read-stealthing viruses), altering disk directory or folder data for infected program files (size-stealthing), or both. For example, the Whale virus is a size-stealthing virus. It infects .EXE program files and alters the folder entries of infected files when other programs attempt to read them. The Whale virus adds 9216 bytes to an infected file. Because changes in file size are an indication that a virus might be present, the virus then subtracts the same number of bytes (9216) from the file size given in the directory/folder entry to trick the user into believing that the file’s size has not changed.

An antivirus program which is not equipped with anti-stealth technology will be deceived.

COMPANION VIRUSES

A companion virus is the exception to the rule that a virus must attach itself to a file. The companion virus instead creates a new file and relies on a behavior of DOS to execute it instead of the program file that is normally executed. These viruses target EXE programs. They create another file of the same name but with a COM extension containing the virus code. These viruses take advantage of a property of MS-DOS which allows files to share the same first name in the same directory (e.g. ABC.EXE and ABC.COM) but executes COM files in preference to EXE files.

For example, the companion virus might create a file named CHKDSK.COM and place it in the same directory as CHKDSK.EXE. Whenever DOS must choose between executing two files of the same name where one has an .EXE extension and the other a .COM extension, it executes the .COM file. This is not an effective way of spreading but has one big advantage - it does not amend files in any way and so can escape integrity tests or resident protection. Another method which can be used by companion viruses is based on defined path. A virus simply puts an infected file into the path listed before the directory within the original program.

PROGRAM VIRUSES

Like normal programs, program viruses must be written for a specific operating system. The vast majority of viruses are written for DOS but some have been written for Windows 3.x, Windows 95/98, and even UNIX. All versions of Windows are compatible with DOS and can host DOS viruses with varying degrees of success. Program viruses infect program files, which commonly have extensions such as .COM, .EXE, .SYS, .DLL, .OVL, or .SCR. Program files are attractive targets for virus writers because they are widely used and have relatively simple formats to which viruses can attach.

Malicious Programs and Scripts

Viruses that infect agent programs (such as those that download software from the Internet; for example, JAVA and ActiveX).

WORM

A worm is a computer program that has the ability to copy itself from machine to machine. Worms normally move around and infect other machines through computer networks. An entire LAN or corporate e-mail system can become totally clogged with copies of a worm, rendering it useless. Worms are commonly spread over the internet via e-mail message attachments and through internet relay chat channels.

For example, the Code Red worm replicated itself over 250,000 times in approximately nine hours on July 19, 2001.

A worm usually exploits some sort of security hole in a piece of software or the operating system. For example, the Slammer worm (which caused mayhem in January 2003) exploited a hole in Microsoft’s SQL server.

Worms use up computer time and network bandwidth when they are replicating, and they often have some sort of evil intent. A worm called Code Red made huge headlines in 2001. Experts predicted that this worm could clog the Internet so effectively that things would completely grind to a halt.

The Code Red worm slowed down Internet traffic when it began to replicate itself, but not nearly as badly as predicted. Each copy of the worm scanned the Internet for Windows NT or Windows 2000 servers that do not have the Microsoft security patch installed. Each time it found an unsecured server, the worm copied itself to that server. The new copy then scanned for other servers to infect. Depending on the number of unsecured servers, a worm could conceivably create hundreds of thousands of copies.

The Code Red worm was designed to do three things:

•Replicate itself for the first 20 days of each month

•Replace Web pages on infected servers with a page that declares "Hacked by Chinese"

•Launch a concerted attack on the White House Web server in an attempt to overwhelm it

The most common version of Code Red is a variation, typically referred to as a mutated strain, of the original Ida Code Red that replicated itself on July 19, 2001.

TROJAN HORSES

Trojans, another form of malware, are generally agreed upon as doing something other than the user expected, with that “something” defined as malicious. Most often, Trojans are associated with remote access programs that perform illicit operations such as password-stealing or which allow compromised machines to be used for targeted denial of service attacks. One of the more basic forms of a denial of service (DoS) attack involves flooding a target system with so much data, traffic, or commands that it can no longer perform its core functions. When multiple machines are gathered together to launch such an attack, it is known as a distributed denial of service attack, or DDoS.

Because Trojan horses do not make duplicates of themselves on the victims disk (or copy themselves to other disks), they are not technically viruses. But because they can do harm, many experts consider them to be a type of virus. Trojan horses are often used as by hackers to create a back door to an infected system. Trojans, such as BackOrrifice are very dangerous. If anyone runs this program and his computer is connected to the internet, then the hacker can take control of that computer - transfer files to or from the computer, capture screen contents, run any program or kill any running process, etc.

Once a Trojan is installed onto the system this program has the same privileges as the user of the computer and can exploit the system to do something the user did not intend such as:

?Delete files

?Transmit to the intruder any files that the user can read

?Change any files that the user can modify

?Install other programs with the user’s privileges

?Execute privilege-elevation attacks—the Trojan can attempt to exploit a weakness to raise the level of access beyond the user running the Trojan. If successful, the Trojan can operate with increased privileges.

?Install viruses

?Install other Trojans

The Following Tips Will Help The User To Minimize Virus Risk:

?If the users are truly worried about traditional (as opposed to e-mail) viruses, they should be running a more secure operating system like UNIX. One should never hear about viruses on these operating systems because the security features keep viruses (and unwanted human visitors) away from the hard disk.

?If the users are using an unsecured operating system, then buying virus protection software is a nice safeguard. Some popular anti virus programs include:

•McAfee Virus Scan

•Norton Anti Virus

•Virex

•PC—cillin

•Avast!

•AVG Anti Virus System

?Automatic protection of anti-virus software should be turned on at all times.

?The users should perform a manual scan (or schedule a scan to occur automatically) of their hard disks weekly. These scans supplement automatic protection and confirm that the computer is virus-free.

?Scan all floppy disks before first use.

?Disable floppy disk booting — most computers now allow the user to do this, and that will eliminate the risk of a boot sector virus coming in from a floppy disk accidentally left in the drive.

?The users should Enable Automatic Update option of their anti-virus software in order to update their virus definition files.

?Creation and maintenance of a rescue disk should be done by the user in order to facilitate recovery from certain boot viruses.

?Periodic backups of the hard disk should be done.

?Users’ should buy legal copies of all software they use and make write-protected backups.

? Email messages and email attachments from unknown people should not be opened. Attachments that come in as Word files (.DOC), spreadsheets (.XLS), images (.GIF and .JPG), etc., are data files and they can do no damage (noting the macro virus problem in Word and Excel documents mentioned above). A file with an extension like EXE, COM or VBS is an executable, and an executable can do any sort of damage it wants. Further it should be verified that the "author" of the email has sent the attachments. Newer viruses can send email messages that appear to be from a person user know.

?The potential users should make sure that Macro Virus Protection is enabled in all Microsoft applications, and they should never run macros in a document unless they know specifically the functionality of the macros.

?Appropriate Passwords should be assigned to the shared network drives.

Things that are not viruses!

Joke programs

Joke programs are not viruses and do not inflict any damage. Their purpose is to frighten their victims into thinking that a virus has infected and damaged their system. For example, a joke program may display a message warning the user not to touch any keys or else the computer’s hard disk will be formatted.

Droppers

A dropper is a program that is not a virus, nor is it infected with a virus but when run it installs a virus into memory on to the disk, or onto a file. Droppers have been written sometimes as a convenient carrier for a virus and sometimes as an act of sabotage.

Hoaxes

There must be very few people on email who haven’t received a chain letter with the subject line warning of a virus doing the rounds. These are often hoaxes and meant to scare people and have fun at their expense. The warnings encourage the recipient of the e-mail to pass the warning to the netizens and thus create an unnecessary furor, besides clogging mailboxes, as it usurps an air of credibility.

Methodology of virus detection applied by antivirus softwares:

Three main methods exist for detecting viruses: integrity checking (also known as checksumming), behavior monitoring and pattern matching (scanning).

Integrity checking

Antivirus programs that use integrity checking start by building an initial record of the status (size, time, date, etc.) of every application file on the hard drive. Using this data, checksumming programs then monitor the files to see if changes have been made. If the status changes, the integrity checker warns the user of a possible virus.

However, this method has several disadvantages, the biggest being that false alarms are altogether too common. The records used by checksumming programs are often rendered obsolete by legitimate programs, which, in their normal course of operations, make changes to files that appear to the Integrity checker to be viral activity. Another weakness of integrity checking is that it can only alert the user after a virus has infected the system.

Behavior monitoring

Behavior Monitoring programs are usually terminate and stay resident (TSR) and constantly monitor requests that are passed to the interrupt table. These programs are on the lookout for activities that a virus might engage in–requests to write to a boot sector, opening an executable program for writing, or placing itself resident in memory. The behavior these programs monitor is derived from a user-configurable set of rules.

Pattern matching

Using a process called "pattern matching," the anti-virus software draws upon an extensive database of virus patterns to identify known virus signatures, or telltale snippets of virus code. Key areas of each scanned file are compared against the list of thousands of virus signatures that the anti-virus software has on record.

Whenever a match occurs, the anti-virus software takes the action the user has configured: Clean, Delete, Quarantine, Pass (Deny Access for Real-time Scan), or Rename.

Self Defense Mechanisms Evolved By Viruses

Virus authors of course wish that their child successfully lives. For this reason there are many viruses outfitted with some self-defense mechanisms against anti virus systems.

Passive Defense :

Viruses use a variety of methods to hide themselves from antivirus programs. Passive defense uses programming methods which make analysis of the virus more difficult, e.g. polymorphic viruses which were developed to counter scanners looking for constant strings of virus code.

Today antivirus systems are capable of analyzing polymorphic code and searching for virus identifiers in the decrypted body. The virus authors reacted by making the encryption too complex for antivirus software to unravel, thus mistaking it for a clean program.

Active Self-defense :

Viruses actively defend themselves by protecting their own code or by attempting to damage antivirus software. A simple method is to locate antivirus software databases and amend or delete them.

More sophisticated resident viruses use stealth techniques. When they detect a request to use an infected file, they can temporarily "clean" it or report its original (uninfected) parameters. They can monitor which programs are being executed and react if it is antivirus software. The list of such reactions is endless. Usually, the execution of the antivirus program is refused, but it could be erased (often accompanied by a bogus error message) or the virus suspends its activities while it runs. There are occasionally extremely ‘clever’ viruses which modify the code of a specific AV program to partially disable it.

There are very rare viruses which consider an attempt to run an anti-virus program as arrogant and immediately reply with some revenge action - for example hard disk formatting.

Trap

A trap is the most malicious form of self-defense and works as follows. Although the user’s computer is infected but everything appears to work correctly. Once the user discovers the virus and removes it things get complicated - programs no longer run properly or the hard disk may become inaccessible even when booting from a clean system diskette.

The best known trap virus is One_Half. It continuously encrypts the data on a hard disk (two tracks on every boot). If it is removed from the partition sector before data files are decoded then some files will become inaccessible. At this stage the situation is serious but recovery of the data is still possible. However, if the user runs a disk utility (Scandisk etc.) to repair the damage then the data will almost certainly be lost forever.

These utilities are designed to repair relatively minor damage to file system and do not recognize the encrypted data.

REFERENCE:

1. Mary Landesman “What is a virus?”

http://antivirus.about.com/cs/tutorials/a/whatisavirus.htm

2. NetGuide “What are computer viruses? “–

http://www.netguide.co.nz/knowhow/tutorials/print.php?iid=38

3. Marshall Brain “How Computer Viruses Work”

http://www.Howstuffworks How Computer Viruses Work.htm

4. AVG Anti Virus Free Edition Help

Developed by Grisoft Inc

5. Norton Anti-virus Help

Developed by Symantec Corporation

6. Trend Micro PC-cillin Help

Developed by Trend Micro Inc

7. Peter Norton “Computer Viruses”

Introduction to Computers, Tata McGraw Hill Co:

8. Dr.Solomon ”About Viruses” &”Virus Prevention”

Dr.Solomon’s Virus Encyclopedia, Dr.Solomon’s Software Ltd.

9. C.A.Schmidt ”Virus”

The Complete Computer Upgrade And Repair Text Book,Dreamtech

10. S.Jaiswal “Virus Detection And Elimination”

Information Technology Today, Galgotia Publication Pvt. Ltd.



HOMER

Samg asked:


I have to computers one with the O/S ME and the other XP home edition. I want to connect the two computers without using the paralell ports. I think i need to create a dial in server but i need help with this on these O/S’s.

CORNELL

dave asked:


I use Windows filesharing and would like to stop one computer on my LAN from accessing anything but other computers on my local network- I do not want it to be able to access the internet.

Can anyone recommend how to do this?
I would like this to be something configured in Windows itself since I do not want all partitions on the computer to be unable to access the internet. Just one of them.

ADRIAN

Boney asked:


I have a Cat 5e cable, RJ45 connectors and 3 computers with network cards. Is it possible for me to network these three computers without using a switch or a router? If the switch has a simple circuit, I can make it my own.

Thank you for helping me on this.

FREDDIE

heartzz_ablaze asked:


We have 3 computers. Each computer freezes up alot and internet explorer has to restart.On my sons computer it completely kills the computer. The cable company said its not on their end. The modem is theirs. The say its my old router,,all so the wallplug is kinda loose where we have them both plugged in at at the wall. My son and I both have vista and the other one is xp. Its not like we get on each others computers to pass a virus.
no dont have the disks,for any of them.

JOSEPH