Everybody is talking about computer viruses, but a virus is just one of many threats for today's computer user. Besides viruses we are also threatened by worms, trojans, spyware, adware and keyloggers. It is clear that we can do without them, but click here for more information on the differences between the various species.

Despite Antivirus program my PC is infected all the same! How is this possible?

For various reasons your PC can become infected, although you installed an Antivirus program. To understand this it's helpful to know how your Antivirus program works. Every Antivirus program consists of a program part and a database with virus definitions. The latter is a collection of characteristics for all known viruses, so they can be recognised. Via the internet virus definitions can be actualised automatically. For commercial Antivirus programs you need a subscription to do so. Usually the subscription has to be renewed after one year, like with Norton or McAfee. Free Antivirus programs - like AVG and Avast - do not require a paid subscription.

Infection can occur when the virus definitions are not up-to-date, either because the automatic update function has been disabled or because the subscription has expired. Furthermore, there are always a few hours (or sometimes even a few days) between the virus outbreak and the corresponding update of the virus definitions for your Antivirus program. So, with a little bad luck, you can get infected in period in between. Finally, comparative tests show that most Antivirus programs only protect you against 92% to 99% of all viruses. Even renowned names like Norton and McAfee can't offer 100% protection.