Antivirus Software, Free Online Virus Scan

The free antivirus programs listed on this page allow you to detect computer viruses, remove or repair infected files, prevent infection, detect and remove email viruses, etc. There are also free online virus scanning services available for those who prefer (or need to) scan for virus that way.

Note that a number of the free antivirus software listed have limited support for scanning spyware and other types of non-virus malware that their commercial equivalents provide. If you are looking for commercial antivirus software, one that comes highly recommended by security-conscious people is the Avira Antivir Premium  (which is very light on resources and consistently has a very high detection rate). Also popular among many computer users is Norton Antivirus,  which also has a Mac OS X version.

If your system is already infected, you may also want to take a look at the Free Antivirus Rescue CDs and DVDs page.

Incidentally, you should not install more than one antivirus or antimalware product on your computer. Even if the software does not complain and all seems fine, there may be underlying conflicts that cause one or more of the software to miss viruses and other malware. That is to say, you may end up with a system that is less secure and more unstable than if you were simply running a single product.

PC Tools Antivirus and ThreatFire Antivirus (Free Editions)   
This vendor provides a free edition of its commercial PC Tools Antivirus program that protects your system against viruses, worms and Trojans. It includes a real-time scanner that checks files that you run (etc). The program detects, quarantines (places infected files in a safe location where it won't infect anything), disinfects (removes virus infections) the malware. Regular updates are free and there is no time limit. (The paid version adds priority updates as well as support.) Also available on that page is ThreatFire Free Edition, an antivirus product that does not work by using signatures to detect malware (such as virus signatures), but operates by providing behavioural ("behavioral" in US English) protection, meaning that it looks at a program's behaviour to figure out whether it is a virus. This allows it to (hopefully) detect new (zero-day) viruses, that is, viruses that have just burst onto the scene and have not been analyzed by antivirus vendors yet.

VIPRE Rescue Program
This is a command line antivirus program that is designed to clean an infected computer. That is to say, it is not designed to be used in place of your normal antivirus program that you run in the background on your computer for your daily work, but it's for systems that are already infested with malware. The latest virus definitions are bundled into the program itself, so only download it when you actually need it so that you can get the latest updated version. The program can be copied to a USB flash drive and plugged into an infected machine and run there (see the instructions on their site for more information). It is a self-contained program (ie, everything you need is bundled into the file you download) and can handle rootkits in addition to the usual malware. This is a subset of the full VIPRE Antivirus software (which of course has the complete graphical interface and can protect against viruses and other malware in addition to cleaning up).

Microsoft Security Essentials
This is a free antivirus / anti-malware tool from Microsoft that is reported to be lightweight and generally unobtrusive. It works on XP, Vista and Windows 7 (both 32 and 64 bit). It handles viruses, spyware, trojans, rootkits and other types of malware.

Avira AntiVir Personal Edition
Avira AntiVir Personal Edition is a free antivirus program for Windows computers. It has a resident component that monitors file movements for signs of viruses. It also allows you to scan your computer and repair files that have been infected. The program comes with a facility to automatically check the AntiVir website for updates to the virus definitions and download them. The free version pops up an annoying banner each time it updates, and may not have the full range of capabilities that the commercial Avira Antivir Premium version does.

AVG Anti-Virus
The AVG Anti-Virus software comprises a resident program that works in the background, an email scanner (checks your email for viruses), an on-demand scanner (eg, you invoke it to scan your system), the ability to repair certain infected files, and automatic updates of the virus definitions. A more fully-featured commercial version is also available.

avast! Home Edition
avast! Home Edition is free for home users on non-commercial computers. You have to register your copy and supply them your email address (get a free email address here if you wish) so that they can send you a license key to activate the program.

Rising Antivirus
Rising Antivirus is a new antivirus software that guards against virus, trojans, worms and rootkits. Besides the usual resident scanner, it also checks your incoming and outgoing email (POP3/SMTP), watches out for hidden processes and malicious behaviour, and has application access control and program startup control (probably meaning some sort of host intrusion prevention system).

Comodo Antivirus
Comodo Antivirus protects your system from viruses, spyware, trojans and other types of malware. It also something they call an Auto Sandbox, based on host intrusion protection techniques. This software is a subset of their full version, Comodo Internet Security Pro.  It is a Windows program.

Clam AntiVirus
ClamAV is a free command line antivirus scanner for Unix systems. You can also integrate it with your mail server for scanning your email messages and attachments. It is able to scan inside archives like RAR archives, Zip archives, Gzip and Bzip2 archives (that is, it has unpacking engines for those types of compressed archives). If you are a programmer, you can even integrate the antivirus scanner into your own programs. This free antivirus program comes with source code that is released under the GNU General Public License. Prebuilt binary packages are available for numerous Linux distributions (Debian, RedHat / Fedora, PLD Linux, Mandrake), Microsoft Windows, FreeBSD, OpenBSD, AIX, OSF and Solaris 8 (Sparc).