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Computer Virus Close-up

by S.K. Tsui

A computer virus is a program that is designed to replicate itself by copying itself into the other programs stored in a computer. There are several types of viruses. The FILE INFECTORS will attach themselves to ordinary program files or document files. They usually infect arbitrary .COM .EXE, .SYS, .OVL, .PRG, .MNU or document files. The SYSTEM or BOOT-RECORD INFECTORS infect executable code found in certain system areas such as the partition table of your hard disk or the boot sector of your floppies. MACRO virus can infect word processing and spreadsheet documents that use macros. It is also possible for HTML documents containing JavaScript, VB Script or other types of executable code to spread viruses or other malicious code.

The damage done depends on how the virus is written. Some may do little or no damage, while some may completely destroy your files or render your machine unusable.

Trojan horse program is often confused with viruses. Actually it is not a virus (because it does not attach itself to other programs), but pretends to be a useful program such as a new release of famous application. When you run it, it may delete files on your hard disk or do other damage to your PC.

Ways of Getting Infected

In order to activate a virus, your computer has to execute the virus program code by booting from an infected floppy, running an infected application, or opening a program attached to an E-mail (or a Word document) with macro embedded.

Will My PC be Infected if I Read E-mail or Surf on the Internet?

In general, reading a plain-text E-mail or HTML message will not infect your computer with a virus. But you have to be very careful in handling messages containing embedded executable code such as JavaScript or VB Script in an HTML message or messages that include an executable file attachment (i.e., a program file or a Word document containing macros). If your mail client or browser has the ability to execute this kind of executable code, then your computer may have a chance to be infected by just reading or even previewing these kinds of messages. VBS/BubbleBoy is the first e-mail worm of this type.

On the other hand, it is safe to open files that the computer treats as pure data. This includes opening graphics and sound files such as .gif, .jpg, .mp3, .wav, and plain text files.

What to Do if My PC Gets Infected

If a virus does infect your PC, you can run the anti-virus program to remove it. Simply follow the instructions of the anti-virus program. If the virus destroys some of your data, you can restore these files from your most recent backup. Remember to check the files you restore to make sure these backups were not infected. If you do not feel comfortable doing it yourself, ask a technical person to do it for you.

General Tips on Avoiding Virus Infections

  1. Backup your data regularly. This can protect your data not only from virus attack, but also from hardware failure. A recent backup may be the only way to recover your data after virus attack or hardware failure.

  2. Install anti-virus software from well-known and reputable companies. Do not forget to update it regularly. It is even better to enable the real-time scanning feature of the anti-virus program every time you boot your system, so that it will check for viruses each time your computer accesses an executable file (but slowing down the program activation time).

  3. Scan any new programs or document files that may contain executable code before you run or open them, especially those files you download from the Internet and the attachments in the document files.

  4. Do not open e-mail and its attachments from unknown source. Delete it immediately if suspicious.

  5. Do not download and run programs from unknown sites.

  6. Do not use piracy software.

  7. Disable the automatically execute JavaScript, VB Scripts, Word macros, etc. feature of your e-mail client and newsreader. Carefully assign the security level of your browser.

  8. Apply patches regularly and timely to the operating system, browser, e-mail client, etc. in order to fix security holes.

Extra cautions need to be taken during holiday seasons especially at Christmas and New Year. These are the high-risk periods for your computer to be infected by computer virus, as people like to send e-mail to each other with greeting cards, pictures or even executable programs attached. If your PC unfortunately gets infected, please contact our Help Desk at ext. 7658 without delay.