About a year ago, we took a look at the growing trend toward open-source security and highlighted 10 of the best apps available. Since then, the area has continued to mature, and now we're back highlighting 75 of the most frequently downloaded open-source security applications.

Anti-Virus/Anti-Malware

1. ClamWin Free Antivirus


This Windows-only app uses the incredibly popular ClamAV engine to detect viruses and spyware. It includes a scanning scheduler, automatic downloads, and a Microsoft Outlook plug-in. However, it does not provide real-time scanning; you'll need to scan your files manually in order to be protected. Operating System: Windows.

2. ClamAV

Numerous commercial and open-source products are based on the Clam Antivirus engine. Designed for protecting e-mail gateways, Clam AV offers automatic updates, a command line scanner, and more. Operating System: Unix, Linux, BSD.

3. Moon Secure Antivirus

Moon Secure is currently based on ClamAV, but the developers are working on an antivirus engine of their own that will enable real-time scanning. Operating System: Windows.

4. Rootkit Hunter

As you might expect from its name, Rootkit Hunter searches your system for rootkits and other unwanted tools. It does not provide live or scheduled scanning, but the Web site contains instructions for setting up your system to run Rootkit Hunter daily. Operating System: Linux, Unix.

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5. AMaVis

Short for "A Mail Virus Scanner," AMaVis acts as a go between for your anti-virus software and your mail transport agent so that incoming e-mails can be scanned for viruses. The site contains the complete—and very extensive—list of supported applications. Operating System: OS Independent.

6. ClamMail ClamMail combines a POP3 e-mail proxy with the ClamAV engine. The result is free antivirus protection for messages accessed via Outlook, Thunderbird, Eudora, or other POP3 apps. Operating System: Windows.

7. P3Scan

This e-mail proxy server scans both incoming and outgoing messages for viruses, worms, trojans, spam, and other malware. Like most open-source anti-virus tools, it's based in part on the ClamAV engine. Operating System: Linux.

8. Viralator

Still getting the occasional network virus even after you install anti-virus software? Viralator supplements the existing anti-virus software on your proxy server to block malware that might otherwise slip in when users access free webmail accounts. Operating System: Linux, Unix.

Anti-Spyware

9. xpy

This tiny program (less than 60KB), improves security, improves performance, and closes some of the flaws which opens up Windows to spyware. It disables the Windows "calling home" features, disarms Internet Explorer, disables Windows Media Player, and more. Operating System: Windows.

10. Nixory

Nixory is designed to protect Firefox users from unwanted cookies and spyware. And unlike most similar programs, you won't need to delete your previously installed anti-spyware or anti-malware programs in order to use it. Operating System: OS Independent.

Communication and File Sharing

11. Mute

Using routing mechanisms inspired by ants (yes, the insects), Mute provides completely anonymous file transfer and file sharing that is virtually impossible to trace. In addition, messages passed on the network are protected by military grade encryption. Operating System: OS Independent.

12. Waste

Waste allows small groups of users to chat and download files securely and anonymously. Transmissions are encrypted using RSA and Blowfish algorithms. Operating System: Windows, Linux, BSD, OS X.

13. ANts P2P

This third generation peer-to-peer network hides your identity and encrypts all transmissions for completely secure communication. And as you might expect, it's also inspired by the behavior of ants. Operating System: OS Independent.

Data Removal

14. Eraser

Want to make sure that file you deleted can never be retrieved? Eraser writes over your files with random data so that no one can snoop into your private files. Operating System: Windows and DOS.

15. Darik's Boot and Nuke

Also known as "DBAN," Darik's Boot and Nuke completely eliminates all of the data on a hard drive. It's an ideal way to clean up an old computer before you donate or recycle it. Operating System: OS Independent.