Computer viruses infect your computer. They are software, and are often attached to other software or documents you might receive. When you run the virus's software or the file the virus has infected, the virus can infect your computer's software.
Once the virus has infected your system, it may automatically send out emails containing more copies of the virus using the address book in your email program. This type of virus is called an Internet "Worm," because it is a self-propagating virus.
Trojan Horses are closely related to computer viruses, but they differ in that they do not attempt to replicate themselves. More specifically, a Trojan Horse performs some undesired yet intended action while, or in addition to, pretending to do something else. A common example is a fake login program, which collects account information and passwords by asking for this info just like a normal login program does.
What kind of Damage can a computer virus do?
Some virus can delete or change files. Some viruses will delete all of your documents, or even reformat your hard drive, making your computer unusable.
Some Virus can release confidential information like credit card information, account numbers, and passwords by emailing it to random email addresses or the address of the virus writer.
Some viruses can slow down your system dramatically.
Some viruses plant monitoring software or change security settings that allow hackers to enter your computer without you knowing about it and steal or control information.
Do not open any files attached to an email from an unknown, suspicious or untrustworthy source.
Do not open any files attached to an email unless you know what it is, even if it appears to come from a friend or someone you know. Some viruses can replicate themselves and spread through email. Confirm that your contact really sent an attachment.
Do not open any files attached to an email if the subject line is questionable or unexpected.
Delete chain emails and junk email. Do not forward or reply to any to them. These types of email are considered spam - unsolicited, intrusive messages that clog up the inboxes and networks.
Do not download any files from strangers.
Exercise caution when downloading files from the Internet. Ensure that the source is a legitimate and reputable one. Verify that an anti-virus program checks the files on the download site.
Update your anti-virus software regularly.
Back up your files on a regular basis. If a virus destroys your files, at least you can replace them with your back-up copy. You should store your backup copy in a separate location from your work files, one that is preferably not on your computer.
Don't use P2P software.
Don't use Internet Explorer, Security claims there are flaws in Internet Explorer that allow malware to infect a computer running using the browser.
Getting a virus on your system is frustrating to say the least, and can be hazardous to the health of your computer. Indeed, today's malicious software can even steal your identity and wreck your hard-earned credit rating.
A virus is a computer program intentionally written and released to spread across computers and networks and disrupt your computing experience. These bad-mannered programs come to your PC through e-mail, the internet, downloaded files and files you open on a CD. Viruses typically work by attaching themselves to another program on your PC, and do not infect the computer until the program runs.