Online Security Scanners

Also Test your defenses online. >> 

There are a growing number of "live" security-related services online. They have two main advantages compared to PC-based tools; they are always up to date (including signatures), and there is little or no software to install on your PC. Of course, a cure may be offered for sale if they find badware. In some cases the cure may be worse than the malady. For that reason, stick with recommended security services.

Online scanning: Scan your computer for malware (free)

There's a vast menagerie of badware: viruses, spyware, adware, Trojans, keyloggers, rootkits, etc. online. Scanners in this comprehensive category screen for all of these critters. However, none of these scanners will find everything. ;-) Most of them will find oodles of "Tracking Cookies", which are almost always benign. :-)

• Panda Software has a new, comprehensive scan service called ActiveScan. Active Scan checks all running processes as well as suspicious files against an extensive malware database. It is widely recommended. ActiveScan is free to use, and if it does find trouble you can register and get removal help for $19.95.
• SpywareGuide.com has an online scan that is similar to ActiveScan.
• ESET Online Scanner is a free tool that you can use to not only scan for, but remove malware from your PC without having to install antivirus software. The scanner uses the same technology and signatures as ESET NOD32 Antivirus, and is always up-to-date.
• Webroot Software provides a free privacy test called "Spy Audit", which scans for spyware. Look for Free Scan / Trials.
• eTrust PestPatrol is another comprehensive online scanner service.
• Trend Micro's Housecall rounds out the list, with a comprehensive scanning service of their own.

If you find your PC is infected, you might want to look at your malware removal options before you proceed.

Proactive scanning services

• LinkScanner | Exploit Prevention Labs (EPL)
  "If you'd rather be safe than sorry, enter the URL of the site or web page you want to visit in the box below. Our free LinkScanner service will visit the URL in a controlled environment on our servers. LinkScanner will inspect it in real-time for whether it is hiding any exploit code and, if so, what exploit."
  I use LinkScanner Pro, which provides automatic inspection without requiring you to go to the EPL site and enter the URL.
• SiteAdvisor | McAfee
  "We test the Web to help keep you safe from spyware, spam, viruses and online scams." Note: SiteAdvisor does not protect against Phishing, as that is a different kettle of phish. {sorry}
• Upload (suspicious) files and get them scanned online: [free]
  Virustotal analyzes suspicious files for viruses, worms, trojans, and all kinds of malware. Just upload the file (it's easy) you want to scan. They use multiple malware engines to scan the file, and then report the results. Jotti is a very similar service.
  Sunbelt Software: "Submit a [suspected] malware sample to our automated sandbox server to see what the malware would do to your computer if it were installed." [note of caution]