Combating Computer Viruses
Computer Antivirus Software

Two basic precautions can assist in keeping your computer virus free - install and use software from trusted vendors and refrain from opening unexpected email attachments. Nearly all email attachments are possible carriers of computer viruses. Some of the most well known viruses were distributed by accessing address books of infected computers and sending email (with attachments) to every name in the address book. Even those from known senders should be treated with caution - email addresses can easily be faked to look as though they are from someone you know.

The infamous Melissa virus that appeared in 1999, which was originally posted on an Internet newsgroup, was distributed in a Microsoft Word document. When downloaded and then opened, the virus found and accessed the users Outlook address book and sent copies of the document, together with the virus, to the first 50 names in the user's address book.

Every computer that received the virus and got infected by it, sent out an additional 50 copies, creating a worldwide slowdown of Internet networks. This snowball effect took only a few hours.

Another well known virus that was also distributed by email was the 'ILOVEYOU' virus of 2000. When opened it replicated itself to every email address in the infected computers address book.

Both the above viruses are two of the more well known of recent years but rather than being a thing of the past, more and more viruses are being found almost on a daily basis.
So what other precautions can users take?

Combating Computer Viruses - Antivirus Software

Antivirus software is obtainable in both commercial and freeware versions with a assortment of features and prices, generally from free to less than $50.

The majority of antivirus software works by examining files as they turn up at the computer and by scanning later at configurable pre-set times. The programs work by looking at each email attachment and downloaded file looking for virus 'signatures'.

If a virus is discovered the user will be alerted and infected programs and attachments can be cleansed of the virus or, if not possible, infected files can be deleted or put into 'quarantine' where they can't be run.

Antivirus Software Updates

Computer viruses are very similar to their biological counterparts. Both come in known, though ever evolving patterns. This pattern is the signature of the virus. Because of this continuous evolution, virus-checking files need to be regularly updated. Updated files contain lists and the characteristics of new signatures.

Most antivirus software will either alert you when the virus checking files are out of date, or automatically refresh signature files with the latest versions.

Users can and do become complacent after installing antivirus software, thinking that they are completely protected and don't need to be concerned about becoming infected.

Aside from the fact that antivirus software is written by humans, who can make errors, vendors can only react to viruses after they're created. By that time, much damage can already have been done. An email attachment or program may be infected with a new type of virus that your software cannot (yet) detect.

Some antivirus software can, to a certain extent, detect virus activity even without being able to identify that particular virus. This is an additional level of protection against the latest viruses, but this should still not allow users to become overconfident.

Always use trusted sources for downloading software and treat any and email attachments with caution.

Other Routes of Infection

Finally, a special note about CDs and DVDs. Whilst CD's and DVD's cannot be written to (those that can are called CD-R's, DVD-R/W or some variation), they can still contain viruses. Users who burn their own CD's or DVD's can accidentally copy infected programs onto the disc. Since CD's can contain files that automatically act when the disc is inserted, it is possible, albeit rare, for viruses to be spread without any additional user action.

Yet again, the moral of the story is to only accept material from those you know and trust, and who practice 'safe file sharing'.