Although commercial Linux antivirus products exist, save your money and start with one of several excellent free utilities instead. Even better, pick one that is not only free but open source: the delightfully named Clam AntiVirus. In addition to binary packages (no compiling necessary) for most major Linux distributions, ClamAV is also available for Windows and Mac OS X.

Ad-Aware is designed to provide advanced protection from known Data-mining, aggressive advertising, Parasites, Scumware, selected traditional Trojans, Dialers, Malware, Browser hijackers, and tracking components. With the release of Ad-Aware SE Personal edition, Lavasoft takes the fight against Spyware to the next level.

With Lavasoft’s all new Code Sequence Identification (CSI) technology, you will not only be protected from known content, but will also have advanced protection against many of their unknown variants. To further protect you, Ad-Aware SE Personal Edition also has the capability to scan and list Alternate Data Streams (ADS) in NTFS enabled volumes. In combination with the new scanning engine, Ad-Aware SE will scan your computer faster and more thoroughly than ever before!

Webmaster: If you have an older PC, get an older version if possible. I am still using a P3 900 and Ad-Aware is frustratingly slow, even with nothing else running.

Spybot - Search & Destroy can detect and remove spyware of different kinds from your computer. Spyware is a relatively new kind of threat that common anti-virus applications do not yet cover. If you see new toolbars in your Internet Explorer that you didn't intentionally install, if your browser crashes, or if you browser start page has changed without your knowing, you most probably have spyware. But even if you don't see anything, you may be infected, because more and more spyware is emerging that is silently tracking your surfing behaviour to create a marketing profile of you that will be sold to advertisement companies. Spybot-S&D is free, so there's no harm in trying to see if something snooped into your computer, too :)

Spybot-S&D can also clean usage tracks, an interesting function if you share your computer with other users and don't want them to see what you worked on. And for professional users, it allows to fix some registry inconsistencies and extended reports

Webmaster: If you have an older PC, get an older version if possible. I am still using a P3 900 and Spybot is frustratingly slow, even with nothing else running.

SpywareBlaster doesn`t scan and clean for so-called spyware, but prevents it from being installed in the first place. It achieves this by disabling the CLSIDs of popular spyware ActiveX controls, and also prevents the installation of any of them via a webpage. This allows you to run Internet Explorer with Active-X enabled, but it will never download or even prompt you for any of the known ActiveX controls. All other Active-X controls or plug-ins will work fine. The SpywareBlaster database contains information on these known spyware Active-X controls and can be updated with the click of a button. The application windows displays a list of all controls that it is able to detect (this is not a list of what was found on your computer). The program cannot detect if you have any of the known objects already installed, but if you do, they will be disabled. The program also allows you to take a snapshot of your computer (certain settings) in its clean state and later revert many changes made by spyware and browser hijackers.