Virus - A computer virus is a self-replicating computer program written to alter the way a computer operates, without the permission or knowledge of the user. Though the term is commonly used to refer to a range of malware, a true virus must replicate itself, and must execute itself. The latter criteria are often met by a virus which replaces existing executable files with a virus-infected copy. While viruses can be intentionally destructive—destroying data, for example—some viruses are benign or merely annoying.
Email Worms - often referred to as mass mailing worms. Infection by an email worm can occur when you open an attachment containing a worm. Often attachments can appear to be harmless as they come from a contact you know, however, that contact's email client may have been infected by the worm. When you open the attachment containing the worm, your email client becomes infected and starts sending the worm to contacts in your address book. The worm can therefore spread throughout the Internet at a great rate.
Trojan Horse - a Trojan horse is a program in which malicious or harmful code is contained inside apparently harmless programming or data in such a way that it can get control and do its chosen form of damage. In one celebrated case, a Trojan horse was a program that was supposed to find and destroy computer viruses. A Trojan horse may be widely redistributed as part of a computer virus.
Web Bugs - a web bug is a small, usually invisible graphic added to a web page, email message or other web-aware document. This technique allows spammers to validate that your email is real and working so they can send you more spam. The small graphic allows spammers to know your TCP/IP address and associate email with that address. With this information, a spammer can find out your ISP, domain and lots of other data.
Malicious Attachment - a serious security risk today is the result of malicious executables through email attachments. A malicious executable is defined to be a program that performs a malicious act, such as compromising a system's security, damaging a system or obtaining sensitive information without the users permission. Overtime there have been some high profile incidents with malicious email attachments such as the ILOVEYOU virus and its clones. These malicious attachments cause significant damage in a short time.
Anti-virus software alone can't protect you from all threats of viruses, scripts, web bugs and other nasties that attack your computer. New viruses and worms are released all the time and anti-virus companies have to quickly write new code to stop these new threats, but can only do so when they have been notified of the new threat. This doesn't help you! You may have already received the virus, or not updated your anti-virus software in time, thereby causing havoc to your computer.
Email worms spread quickly across thousands of computers so that widespread damage and embarrassment can easily occur. Don't wait until your anti-virus software is updated - use Benign software to neutralize all future attacks!.
