We're very impressed by the collective smarts of the security community and we highly recommend reading the whole list and investigating any tools you are unfamiliar with. Click any tool name for more details on that particular application, including the chance to read (and write) reviews. Many site elements are explained by tool tips if you hover your mouse over them. Enjoy!
Malwarebytes' Anti-Malware is a malware scanner for Windows. The authors claim to use a variety of technologies to find malware undetectable by other malware scanners. There is a free trial with limited options and a supported full version with the ability to run scheduled scans.
Read 5 reviews.
Latest release: version 18.104.22.1680 on April 9, 2013 (8 months, 1 week ago).
ClamAV is a powerful AntiVirus scanner focused towards integration with mail servers for attachment scanning. It provides a flexible and scalable multi-threaded daemon, a command line scanner, and a tool for automatic updating via the Internet. Clam AntiVirus is based on a shared library distributed with the Clam AntiVirus package, which you can use with your own software. Most importantly, the virus database is kept up to date. The project was acquired by Sourcefire in 2007.
Review this tool.
Latest release: version 0.97.8 on April 23, 2013 (7 months, 3 weeks ago).
VirusTotal is a web service that analyzes submitted files for known viruses and other malware. It incorporates dozens of antivirus engines from different vendors, updated regularly with new signatures. Participating antivirus vendors can get alerts when a file is not detected by their product but is by someone else's.
Read 3 reviews.