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Computer Viruses and Antivirus Software


Here you will find the following explanations and advice regarding computer viruses and antivirus software:



What are computer viruses and what kind of damage can they do to a computer?

Computer virus is a programme that is not orientated towards the computer user and its actions do not serve the interests of computer user. The virus is meant to disrupt the work of the computer, corrupt the data stored on the hard disk, create access rights for other users/hackers, collect passwords and forward them, etc. The computer viruses can also slow a computer network down to a standstill by creating excess network traffic.

The viruses that spread by e-mail send virus-infected e-mails to a random e-mail address from a random sender.

The so-called printer viruses have also started to spread. These viruses search for a non-password-protected printers in a computer network and try to use up all the paper in a printer.

Many viruses activate on a specific date or under specific conditions and can do irreparable damage by corrupting the computer's BIOS ROM and/or all the information on the hard disk.


How do computer viruses spread?

Unlike flu, the computer viruses spread in any time of the year. They spread with files on floppy disks and CD-s, also via computer networks by e-mail and shared resources, using the so-called security holes.

Many computer users have discovered at one moment that their files have been corrupted and the data cannot be restored, or that the computer is acting weirdly and does not allow carrying on with the normal daily work. Very often these situations are caused by computer viruses.

The primary indicators that a computer has been infected by a virus are the following:
• Some programmes work slower.
• The file sizes rise (especially for editable files).
• The appearance of suspicious files that did not exist before.
• A significant decrease in available system memory compared to the normal work situation.
• The appearance of unexpected video and/or sound effects.

In case you detect any of the abovementioned symptoms or other suspicious occurrences (unreliable working conditions, frequent spontaneous reboots etc.) while using your computer, we advise you to immediately check your computer for viruses.


What should be done to avoid computer viruses?

Check that your Windows or other operating system has installed the latest security patches or updates.


  • When using Win95, 98, ME, and XP go to the Windows Update website, the most important updates being the ones labelled Critical updates.
  • Administrators of NT and Win2k systems should definitely check that the latest service pack has been installed on the computer. In the case of NT 4, the cumulative hot-fix pack and IIS updates should also be installed.

Configure your Windows so that you can see the file name extensions. As a rule, these are 3-letter abbreviations, based on which Windows understands whether it is dealing with a Word document (.doc) or a programme (.com, .exe, .bat, .vbs, .pif). If you are sent anything resembling a programme file, do not open it.

To allow the displaying of file name extensions, open any folder, My Documents for example and select Tools/ Folder Options, then View and remove the check from the Hide extensions for known file types checkbox. Now you can always see if you have received a Word document or a malicious virus.

Treat e-mail attachments with caution even if the sender is someone you know. The attachment may have been sent by a virus in his/her computer without the owner's knowledge. If the message in the e-mail does not explicitly state why the e-mail contains an attachment and that it is indeed the wish of the sender to open this attachment, please phone the sender and confirm the intentions. When you are attaching a file to an e-mail yourself, you should add a description of what files are in the attachment and why - the recipient will feel safer opening it.

The files spread in internet newsgroups and chat rooms should be treated with an even greater degree of caution.

Use a personal firewall to protect your computer from hackers and internet worms looking for security holes, but also in order to block the viruses that have already infected your computer from communicating with the outside world. You can download a free ZoneAlarm firewall meant for personal use from the following address: http://www.zonelabs.com.

Be sure to use antivirus software!


Antivirus software

In order to secure your files and for the sensible use of your working time you should use antivirus software in your computer. Although these do not offer a 100% guarantee that your computer will not be harmed by viruses, they do help to detect and remove the majority of computer viruses that are spreading at the moment.

Antivirus software is useless, if it does not update its virus definitions at least once a day, because the newest viruses spread in a day's time. For example, the Nimda virus infected 2,2 million computers in one day. It only took two to three hours for the manufacturers of antivirus software to make the necessary adjustments to their software.

The University of Tartu has bought a Symantec Antivirus license for all its computers. SAV site-license automatically extends to all the home computers of the employees and faculty members. This means that for each license bought for an office computer, the software can also be installed in one home computer. The licenses are valid for 1 year and must be updated yearly.

Here you will find the Installation guide for the Symantec Antivirus. For more information about the licenses purchased by the structural units, please contact the IT-department (Riina Reinumägi, riina [ät] ut [dot] ee).

Other known antiviruses include Norton Antivirus, F-Secure, McAfee and Norman.

Free antivirus software has lately become a rare occurrence. Nevertheless, it is possible to download the free antivirus software AVG 6.0 Free Edition from the AVG AntiVirus page at http://www.grisoft.com/ . In addition, free antivirus software for personal use called AntiVir Personal Edition can be downloaded from http://www.free-av.com. The full version of the same software can be purchased from http://www.hbedv.com.

If a virus has already infected a computer, it is often not possible to install antivirus software in it. In such a case you should run the F-Prot antivirus software from the samba disk on the math server. To do this in a Windows computer, open the Start menu, click Run and enter the following text into the Open text field in the new window: "math.ut.eesambaF-prtf-prot.exe".


Conclusion

This is a suitable place to remind you that when working with a computer, the rule-of-thumb is "better safe than sorry". This means the following:

  • always make backup copies of your files,
  • check all floppy disks, CD-s and files downloaded from the internet for viruses,
  • do not allow your computer to be used by random acquaintances,
  • update your antivirus software at least once a month.