Trojan, Virus and Worms

Computer viruses hide within other programs or documents and spread once you take action of some kind, for example opening an attachment. They come in many forms, and you don't need to install a program for your computer to be infected. For example, some viruses are spread when you open a word-processing document, particularly if you have macros enabled. Once your computer is infected, the virus may attach itself to outgoing files or may be sent as an email attachment.

A Trojan horse is a program that disguises itself as another program. Similar to viruses, these programs are hidden and usually cause an unwanted effect, such as installing a back door in your system that can be used by hackers. In contrast to viruses, they’re not usually designed to replicate.

Worms spread without any user interaction, typically by exploiting a flaw in popular software. Once activated, they generally use the Internet or your LAN (local network) to self-propagate and often take advantage of vulnerabilities in Microsoft Outlook and Microsoft Outlook Express email programs.

Helping to keep you and your computer safe.

Here are some ways to protect yourself and your computer against these programs:

Use anti-virus software like the software that can be found in Yahoo! Mail.

Download anti-virus software updates frequently. They are usually posted weekly, and generally only take a couple of minutes to download.

Scan email attachments and programs downloaded from the Internet. Yahoo! Mail lets you use Norton anti-virus software to scan your attachments before downloading them to your computer (learn more). If a virus is detected, it will clean it for you. If you receive attachments you aren't expecting or from someone you don't know, do not open the attachment. Even if you know the sender, you should scan the attachment.

Turn off the feature in email programs that automatically opens attachments.

Don't install unfamiliar programs. Unless you know exactly what a program does and how it will affect your computer, don't install it.

Carefully read pop-up warnings. Many unscrupulous companies use pop-up advertising that falsely appear to be warnings. The pop-ups (which appear on sites other than Yahoo!) encourage users to install corrective software. These pop-ups should be ignored.

Verify email warnings. You may receive an email warning that claims to be from a computer "expert" warning you of a virus. Such emails usually instruct you to take certain steps to protect your computer. These are usually a hoax -- before following the steps outlined in any email, research it online by searching for Computer Virus Hoax in Yahoo! Search.