Virus scanners work by searching harddisk for files which might be infected by a virus. This method of course is never 100% secure, since only known viruses (or known virus patterns) are detected. If an infection has been detected in a certain file, the virus scanner might be able to clean the file. In that case, you can try another scanner to clean the file, you can try to replace the file or - as a last resort - delete it.

Studies have shown that the effectiveness of Antivirus software is much reduced from what it was a few years ago, particularly against unknown or zero day threats. The German computer magazine c’t found that detection rates for these threats had dropped to a frightening 20% to 30%, as compared to 40% to 50% only one year earlier. Only one product managed a detection rate above 50%.

The problem is magnified by the changing intent of virus authors. Some years ago it was obvious when a virus infection was present. The viruses of the day, written by amateurs, exhibited destructive behavior or popped-up screen messages. Modern viruses are often written by professionals, financed by criminal organizations. It is not in their interests to make their viruses evident, because their purpose is to create botnets or steal information for as long as possible without the user realizing this; consequently, they are often well-hidden. If an infected user has a less-than-effective antivirus product that says the computer is clean, then the virus may go undetected. As a result of this, even major antivirus products have failed to detect programs containing malicious behaviour.

AVG AntiVirus

System: Windows 95/98/Me/NT/2000/XP/Vista/Linux
Licence: Freeware for non-commercial use.

Antivirus protects against viruses, worms and trojans.

• 100% virus detection — AVG’s scanning engine has received numerous awards for its excellent detection of “in the wild” viruses, including the VB100% award. Its unique combination of detection methods provides full protection against viruses, worms, and trojans.
• Full on-access protection — The powerful AVG Resident Shield provides maximum protection by scanning every file opened, executed, or saved. It also prevents the opening or executing of infected files.
• Full e-mail protection — The AVG Personal E-mail Scanner checks every e-mail sent or received, providing full protection from e-mail-borne threats. AVG supports all leading e-mail clients, including MS Outlook, The bat!, Eudora, and all other SMTP/POP3-based e-mail clients, such as Outlook Express. Encrypted connections using SSL are also supported.
• Automatic threat handling — AVG can automatically heal or remove infected files and other threats such as trojans and worms.

HomePage: http://free.grisoft.com/doc/avg-anti-virus-free/
Reviews:

• Cyber Top Cops (2007)
• IT Reviews (2007)
• CNET - First Look (video 2007)
• CNET - Special Features (video 2007)

Avast! 4 Home Edition

System: Windows 95/98/Me/NT/2000/XP/Vista
Licence: Freeware for non-commercial use.

(Full version after free registration)

• On Demand Scanner - with Skinnable Simple Interface - just select what do you want to scan in which way and press the Play button.
• On Access Scanner - resident scanning of all files being opened, read and written and behavior blocker monitoring dangerous actions of viruses.
• E-mail scanner easily integrates with most mail clients and it checks both incoming and outgoing mails, it provides heuristic analysis of mail content to protect against new Worms.
• Network Shield - scans traffic for malicious content - lightweight Firewall.
• Resident protection for IM programs (e.g. MSN Messenger, ICQ) and P2P programs (e.g. Kazaa, DirectConnect).
• Boot Time Scanner - scans disks in the same way and in the same time as Windows CHKDSK does (on NT/2000/XP only).
• Explorer Scanner - right click on the object allows you to scan it.
• Screen Saver Scanner - scans PC during your coffee breaks.
• Virus Chest - safety isolated folder to store infected, suspicious and even some system files - to restore them.

HomePage: http://www.avast.com

Reviews:

• PC Magazine (2005)
• CNET (2007)
• CNET - First Look (video 2007)
• Cyber Top Cops (2007)
• Dooyoo (2006)

ThreatFire 3

System: Windows 2000, 2003, WinXP
Licence: Freeware

ThreatFire is an easy to use antivirus designed to protect computer against malware, trojans, spyware, rootkits, keyloggers, and buffer overflows by intelligently detecting and blocking behavior consistent with that of malware. ThreatFire does this by monitoring system and analyzing programs and process activity. Whenever ThreatFire detects any unusual process or activity, it will display an alert with further information on the threat. If it is a known threat, then antivirus will automatically quarantine the malware and no further action is required on your part. If the threat is unknown, or new, then ThreatFire will display an alert and prompt you to Allow or Quarantine the process. All alerts provide detailed information to help you make an informed decision.

• Persistent zero day threat protection made easy for everyone
• ThreatFire includes advanced protection features including malware quarantine and removal, rootkit scanner and custom rules settings in both the Free and Pro versions.
• Protects against both known and zero-day viruses, worms, trojans, buffer overflows, rootkits.
• Ready for the next malware outbreak, with no signature updates required.
• ActiveDefense technology intelligently scans and analyzes computer processes to detect and block any malicious activity.
• Works alongside your current security programs — there is no need to uninstall your antivirus, anti-spyware, firewall or other security program before installing ThreatFire.
• Runs in background without impacting system performance.

HomePage: http://www.threatfire.com

Review:

• PC Magazine (2007)
• PC Magazine (full article 2007)
• Download.com (users review 2007)

Avira AntiVir PersonalEdition Classic

System: Win98, WinME, WinNT 4.x,Windows 2000, WinXP
Licence: Freeware

It constantly and rapidly scans your computer for malicious programs (such as viruses, Trojans, backdoor programs, hoaxes, worms, dialers etc.), monitoring every action executed by the user or by the operating system and being able to react promptly when a malicious program is detected. Actions include repair, delete, block, rename and quarantine programs or files. This antivirus also features enhanced protection against unknown boot-sector viruses, issuing alerts for boot sectors suspicious formats. Through the permanent update of the detection engine, the protection is ensured constantly: the user can set the product to download any updates when available, thus keeping you clean and safe.

• Extensive Malware Recognition of viruses, Trojans, backdoor programs, worms, etc.
• Automatic updates of antivirus signatures, engine and entire software
• Permanent virus protection, with Virus Guard real time monitoring
• Install and configuration in just a few steps, setup to protect your PC in minutes
• Virus protection against known and unknown threats, using an advanced heuristic system
• Scheduler where you can set the scanner to make automatic virus scans or updates on your system

HomePage: http://www.free-av.com

Review:

• Download.com (2007)
• Soft32.com (2007)
• Soft.Bitcomet.com (2007)

PC Tools AntiVirus Free Edition

System: Windows 2000, WinXP, Vista
Licence: Freeware

PC Tools AntiVirus Free Edition is an anti-virus scanner, that provides real-time protection against viruses, worms and Trojans. It also offers on-demand scans, as well as automatic updates and real-time scanning of incoming and outgoing mail. Other features include heuristic scanning and scheduled scans. The Free Edition offers limited support and non-priority updates.

• Protects your PC as you are working, surfing and playing
• Detects, quarantines, disinfects and destroys Viruses, Trojans and Worms
• OnGuard™ protects your computer against threats in real-time
• Automatically checks for frequent updates against the latest threats

HomePage: http://www.pctools.com/free-antivirus/

Review:

• Look at: ThreatFire above

Free antivirus - BitDefender 10 Free Edition

System: Windows 98/Me/NT+SP6/2000/XP/Linux
Licence: Freeware

• Virus scanning and removal On demand scanning - Powerful scan engines ensure detection and removal of all viruses in the wild every time you need it.
• Scheduled scanning The Scheduler lets you plan ahead, and schedule full system/drive scans in the off hours, when you won’t be using your computer.
• Immediate scanning With just a right click you can check your files and folders.
• Skinable interface You can express yourself, designing new interfaces, or you can use those drawn by others.
• Quarantine By isolating the infected files in quarantine, the risk of getting infected diminishes. You also have the possibility to send these files for further analysis to BitDefender Labs.
• Reports When launching a scan you may choose to create a report file where you can see statistics about the scan process.

HomePage: http://www.bitdefender.com

Review:

• PC World (2007)

ClamWin Free Antivirus

System: Windows 98/Me/2000/XP/2003
Licence: Freeware

Includes scheduler, virus database updates, standalone scanner, context menu integration to MS Windows Explorer and Addin to MS Outlook. Also features easy setup program.

• Submit undetected virus and spyware samples.
• Test the latest release, find and submit bugs and feature requests.
• Improve the documentation.
• Promote ClamWin Free Antivirus on the Internet and in the press.
• If you are a C++ or Python developer and have some time to spare you may join the ClamWin Free Antivirus Project and help to improve it
• Or please click on a button below to make a donation and support further development of ClamWin Free Antivirus.

HomePage: http://www.clamwin.com
Review:

• Ebswift.com
• Download.com (users reviews 2006-2007)
• InformationWeek (2006)
• ClamWin Portable Version (USB or Removable Drive)
• How to use ClamWin on portable drive

Comodo AntiVirus Free

System: Windows 2000/Windows XP (SP2)
Licence: Freeware

Comodo AntiVirus leverages multiple technologies (including on demand & on access scanning, email scanning, process monitoring, worm blocking and host intrusion prevention) to immediately start cleaning or quarantining suspicious files from your hard drives, shared disks, emails, downloads and system memory.

• Detects and eliminates viruses from desktops and networks
• Antivirus constantly protects with real-time On Access scanning
• Proactive Heuristic analysis intercepts unknown threats
• Host Intrusion Detection blocks malware before it can run
• Daily, automatic updates of virus definitions

HomePage: http://antivirus.comodo.com
Review:

• Free Thoughts with users’ comments (2006-2007)

Rising Antivirus 2009 Free

System: Windows 98/Me/NT/2000/XP/2003/Vista
Licence: Freeware
RISING Antivirus Free Edition protects, detects and removes local viruses, variant viruses, Trojan horses and malicious programs with Rising Antivirus. Files, e-mails, memory and Web pages are under the all-in- one real-time monitoring system.

• Zero day protection: Rising Cloud Security users communicate with the Rising virus lab to form a rapid response network which quickly catches Trojans and other malware.
• Antivirus & Antispyware Protection: Protection from Trojans, worms, rootkits and other malware. With unparalleled expertise in combating malware, Rising offers you actual protection against today’s cyber threats without putting a strain on your computer’s resources.
• File Monitor: Automatically detects viruses in active files and prevents them from infecting your computer.
• Email Monitor: Scans inbound (POP3) and outbound (SMTP) emails for malware.
• Application Control: Monitor the operational status of applications and block suspicious activities
• Web Trojan Defense: Automatically blocks malicious web scripts and viruses while you are browsing the web.

HomePage: http://www.freerav.com/

McAfee VirusScan Plus - Special edition from AOL

System: Windows 2000/Windows XP/Vista
Licence: Freeware

• AOLParental Controls: Software designed to give parents the tools they need to help protect their children from inappropriate or dangerous online material. Easy-to-use features of the software include standard age-based access controls, as well as specific controls on IM and chat, online timers, and e-mail reports on children’s online activities.
• Computer Check-Up: Automatically scans for and fixes more than 30 PC and Internet problems.
• Active Security Monitor: An easy way for consumers to know if they are protected from computer viruses, spyware, identity theft, network intrusions and other security threats, the Active Security Monitor offers quick fixes and recommendations for resolving security vulnerabilities.
• Phishing Protection: People using AOL® 9.0 or another recent version of the AOL software (also available free) will get automatic protection from known phishing sites thanks to reports from millions of AOL users and several Internet-monitoring firms.
• Spam Protection: AOL® Mail blocks more than 1 billion pieces of spam each day, and gives users the ability to block junk mail by keyword or sender; report spam; and manage their own spam folders.
• Web Pop-up Controls: AOL’s pop-up controls let users choose which pop-up and animated ads they want to see online, as well as tame animated Web ads when they are using the AOL software.

HomePage: http://safety.aol.com/isc/BasicSecurity/
Review:

• Softpedia (2007)
• LiewCF (2007)

Google Pack Software

System: Windows 2000/Windows XP/Vista
Licence: Freeware

Includes:

• Spyware Doctor Starter Edition Detects and removes spyware, adware, trojans and keyloggers Includes Smart Updates and scheduling to protect your PC
• Norton Security Scan Detects and eliminates viruses and internet worms Free detection updates and scheduled scanning

HomePage: http://pack.google.com

GentleSecurityWall

System: Windows 2000/XP/2003 Server/Vista
Licence: Freeware

GentleSecurityWall ensures safe use of internet and network services. Antivirus enforces mandatory access control policy, which maintains confidentiality of your data, prevents damage from intrusions and malicious software: viruses, worms, spyware, key loggers etc. Underlying technology bridges strong GeSWall security with great usability. Being non-intrusive for a user GeSWall requires no or minimal configuration and enforces protection once installed.

• Prevents key loggers, rootkits, backdoors.
• Prevents confidential file disclosure.
• Prevents targeted intrusions.
• Prevents malicious software infection.
• Independent of attack techniques.
• Easy to use, non-intrusive.

HomePage: http://www.gentlesecurity.comBlog: http://www.gentlesecurity.com/blog/

Sentinel

System: Windows 95/98/Me/NT/2000/XP/2003
Licence: Freeware

Advanced file integrity checker that integrates seamlessly with your anti-virus/trojan application(s).

• Audits your system folder (as well as upto 20 other folders) for the slightest file changes and/or additions. If any files fail the integrity check, your anti-virus/trojan program will be notified
• The RegWatch portion of Sentinel will warn your anti-virus program of programs that are trying to start up using the Registry
• Shut Down your computer with confidence that no viruses or trojans will attempt to corrupt your system. This feature will automatically perform an Integrity Check and a Registry audit - all files that have been changed or modified will be scanned by your anti-virus scanner.
• Logs every file that Sentinel sends over to your anti-virus scanner; every log can be re-scanned with ease
• Integrates seamlessly with most antivirus/trojan applications (upto two at one time)

HomePage: http://www.runtimeware.com
How To: http://www.runtimeware.com/antivirussupport.html

V-Buster

System: Windows 3.x/95/98/Me/NT/2000/XP/2003, DOS
Licence: Freeware

• The solution to worms and trojans with read only files
• Antivirus can read and write to an inaccessible hard disk or diskette. Can also rebuild the Boot Sectors of diskettes and the Boot Sector and Partition Table of a Crashed Inaccessible Hard Disk
• Destroys ten of thousands of boot, file and macro viruses, as well as trojans and worms
• Creates rebuild.dta containing pointers of a file, allowing V-Buster to rebuild any file by any virus, known or unknown
• Rebuilds files infected by mutating viruses
• Detects the presence of memory, boot & partition table viruses
• Detects and rebuilds files infected by winword and excel macro viruses
• Can monitor a computer for viral activity and detect the presence of any virus in any file, known or unknown
• Provides utilites, switcheable mode functions and GUI interfaces
• Vbuster.exe can be used to search for a file with the option of renaming or deleting the file regardless of the attribute or changing the attribute of the file
• Free online updates of vbuster.exe for new viruses

HomePage: http://vbuster.net
Review:

• Melbourne PC User Group