To prevent malicious programs like trojans, worms, dialers, keyloggers etc. from causing problems in your organization, antivirus software should be installed. Below is a quote from Wikipedia about that the antivirus software is:
Antivirus software (alternate spelling anti-virus) mainly prevent and remove computer viruses, including worms and trojan horses. Such programs may also detect and remove adware, spyware, and other forms of malware.
This post describes the free antivirus scanners that could be installed on a small Windows servers and workstations.
A-squared Free is loaded with features and is available for home users at no cost. In addition to detecting and removing viruses, a-squared also detects spyware, adware, keyloggers, trojans, backdoors, worms, bots and dialers. This free version is the little brother of a-squared Anti-Malware and contains only the scanner to clean infected computers. But it does not come with a background guard, Auto-Update, scheduled scans and HiJackFree.
AVG Free gives you great protection against known viruses and spyware, and tells you when a web page you plan to visit is poisoned. It is only available for single computer use for home and non commercial use. Note that AVG Anti-Virus Free does not work with server operating systems.
Free antivirus software providing desktop security and data protection. avast! detects and removes all forms of malware, including spyware, rootkits and trojans. Free for home users.
Avira AntiVir Personal – is a reliable free antivirus solution, that constantly and rapidly scans your computer for malicious programs such as viruses, trojans, backdoor programs, hoaxes, worms, dialers etc. Monitors every action executed by the user or the operating system and reacts promptly when a malicious program is detected.
Avira AntiVir Personal is a comprehensive, easy to use anti-virus program, designed to offer reliable free of charge virus protection to home-users, for personal use only, and is not for business or commercial use. Available for Windows or Unix.
AVZ Antiviral Toolkit is a freeware application designed to delete adware and spyware modules, network worms, trojan horses (Trojan, TrojanDownloader, TrojanSpy) and Dialers. The utility implements specialized algorithms for detecting keyloggers, finding and blocking rootkits. The toolkit is developed by a russian named Oleg Zaytsev. It started off as an independent anti-viral toolkit but Oleg went to Kaspersky, so now it is Kaspersky’s property.
BitDefender Free Edition uses the same ICSA Labs certified scanning engines found in other BitDefender products, allowing you to enjoy basic virus protection for no cost at all. It is an on-demand virus scanner, which is best used in a system recovery or forensics role.
Comodo Internet Security has all the functionality of a paid AV without the price. It eliminates ALL known Viruses, Worms and Trojans from desktops and networks with no license fees or hidden costs. The product is the all-in-one security software that keeps your computer completely safe from viruses and internet threats. The software is free for life and incorporates Comodo Firewall and Comodo Antivirus. If required, either product can be installed individually during setup.
ClamWin Free Antivirus comes with an easy installer and open source code. You may download and use it absolutely free of charge. It features: high detection rates for viruses and spyware, scanning scheduler, automatic downloads of regularly updated virus database, standalone virus scanner and right-click menu integration etc.
Panda Cloud Antivirus protects you while you browse, play or work and you won’t even notice it. It is extremely light as all the work is done in the cloud. The anti-virus provides you with the fastest protection against the newest viruses thanks to its cloud-scanning from PandaLabs’ servers.
Dr.Web CureIt! is a FREE anti-virus and anti-spyware utility based on Dr.Web Anti-virus scanner, which will help you quickly scan and cure OS without installation of the Dr.Web Anti-virus. The utility contains the most up-to-date add-ons to the Dr.Web virus databases going up to twice per hour frequency at periods of high malware submissions.
RemoveIT Pro is a security software that allows you to protect yor PC by locating & removing many new dangerous files including spyware, malware, virus, worms, trojan's and adware that other popular antivirus programs do not find.
ThreatFire is zero-day security software designed for the average consumer. ThreatFire protects in real-time against viruses, worms, trojans, spyware, adware, rootkits, keyloggers, and buffer overflows. It is designed to be used alongside your current anti-virus to protect you between anti-virus updates. Because it is behaviour-based and not signature-based, ThreatFire protects against both known and unknown, or zero-day, threats. It is easy to install, painless to use, and immediately effective against today's computer security threats. And best of all, ThreatFire is free to all home users.