A computer virus is similar to a virus that affects living organisms in that it can spread from computer to computer, infecting each new host with a small program that is intent on causing some kind of harm.  The infection may be relatively harmless such as a prank popup display, or it can be extremely dangerous if its intent is to destroy all the data on your hard drive.
Staying true to its nature, a virus will also attempt to spread to other PCs by various means such as file sharing websites, thumb drives or email.  A virus is typically very small and can imbed itself in already existing system files on your PC, or create innocent looking files or registry entries that are difficult to locate and destroy.  Most viruses are also smart enough to resist many methods of removal.

There are several ways in which a virus can infect your system.  Infected email attachments is the most common source of infection. These attachement may be an image, a document or just about any other type of file that can be attached to an email. Infections are also spread through internet file sharing and download sites.

Types of Threats

• Worm – a self-replicating program which uses the system to send copies itself to other systems with no user intervention
• Spyware – a program that becomes installed on a system which collects small bits of information about the system or user without their knowledge
• Adware – a program that displays or downloads advertisements to a PC.  The ads may appear as a popup, or may appear in a portion of the web browser
• Malware – a broad term for a wide range of malicious software whose intent is to disrupt your system, gather information about the system or gain access to system resources. Malware is not necessarily the virus but is often the method of transmittal
• Trojan Horse – a program that masquerades as a safe application yet contains malicious code that will cause an infection.
• Rogue Software – decieving or misleading programs that trick users into paying for an unnecessary or fake security software

Antivirus Software

Programs that are designed to detect and remove or neutralize viruses are referred to as Antivirus Software.  They work by periodically scanning your system for known viruses and also by monitoring all new files being added to your system.

How Can You Tell If Your PC Is Infected

The existence of one or more of the following may be an indication that your system is infected:

• Random pop-ups- Unknown files or icons appearing on your desktop or other places when you did not install them
• Files or icons disappearing from your system without you having uninstalled or moved them
• Unusual error messages
• Hardware devices (hard drives, CD Drives, etc) can no longer be accessed
• Applications crash unexpectedly, run slowly or don’t start up at all
• Your system becomes unstable and freezes or crashes frequently
• Your system will not boot up at all

Virus Prevention

Prevention is the best approach to maintaining a healthy system.  Installing a reputable Antivirus program is your first priority.  The program you install must update itself frequently with files that contain lists and characteristics of the most recent viruses that are circlating.  In addition to the Antivirus program, maintain healthy habits with regard to your online and email activities.- Never download attachments from email accounts that you do not know.

• Only download files from trusted sites
• ensure that you have a good firewall between your network and the internet
• update your PC with the latest updates as they are released