Trend Micro™ HouseCall is an application for checking whether your computer has been infected by viruses, spyware, or other malware. HouseCall performs additional security checks to identify and fix vulnerabilities to prevent reinfection.

AVG Technologies' AVG Anti-Virus Free Edition, compatible with Microsoft Outlook and Eudora, quarantines suspected virus-infected emails and scans all email traffic over POP3 and SMTP protocols.

Ooka™ provides this service free to hundreds of thousands of people every day. If you are experiencing slowness with your Internet connection or are simply interested in testing your speed, this online speed test is for you.

This product is considered to be one of the best vulnerability scanners available at any price — and it happens to be free. The tool explores and maps network systems for potential weaknesses that could provide an open door to attackers. The Nessus client is compatible with all Linux/Unix systems. There's also a Win32 GUI client that works with any version of Windows.

This no-cost program scans computers for hidden parasites — including Trojan horses, worms and spyware — and removes them permanently. Ad-Aware Free is perhaps the most popular free security tool in Internet history, with publisher Lavasoft reporting more than 250 million downloads so far.

Are you sick of spam clogging your employees' mailboxes? POP3-compatible MailWasher promises to filter and block spam messages while allowing legitimate email to pass through unimpeded. And it won't cost you a nickel.