Online browser-based virus scanners The scanners listed below can scan your whole computer. Most of them require that you visit with Internet Explorer, since they use Internet Explorer's ActiveX capabilities to perform the virus scan. These scanners can give you a "second opinion" if you suspect your present antivirus software isn't detecting an infection. Don't expect miracles; they may not be able to remove all the malware even if they detect it.

• To accompany any of the scanners below, I strongly recommend you check your system for known vulnerabilities with Secunia's online checkup. This is getting to be quite imporant nowdays.

• F-Secure online scanner Scans for viruses/worms/trojans, spyware and rootkits

• Panda ActiveScan Removes viruses/worms/trojans, detects spyware

• TrendMicro Removes viruses/worms/trojans and spyware, also checks whether the computer is missing important security patches

• Symantec Scans for malware, no removal capabilities

• Microsoft Live OneCare Safety Scanner Scans for viruses/worms/trojans, spyware, a few open ports, disk fragmentation, and Registry errors. OneCare hasn't had good detection in the past, but is actually showing some improvement lately.

Online single-file scanners These scanners scan one file at a time using many antivirus products. Upload the file and take a snack break : ) while they generate the results. Do not assume that a "clean" result means the file is safe, however!

• VirusTotal.com Currently scanning with about 30 different security softwares. 10MB maximum file size.

• Jotti online scanner 15MB maximum file size.

Online port & security scanners Does your computer "answer the door" when strangers knock? Find out.

• McAfee Wi-FiScan wireless security scanner
• Symantec online port scanner, use Internet Explorer
• ShieldsUP! port scan at GRC.com

Spyware/adware resources Adware and spyware are often installed by Trojans or Downloaders, so use current-generation antivirus software to ensure you're getting to the root of the problem. If you need good antivirus software, I suggest Kaspersky, configured as shown here. Update your antivirus and anti-spyware software, and then reboot into Safe Mode and run antivirus and anti-spyware scans (to access Safe Mode, press the F8 key repeatedly when the first WindowsXP boot screen is just about to show).

• For advanced spyware-removal situations, John has a malware-removal guide here.

• WinSockFix for Win2000/WinXP Before you start removing spyware, download WinSockFix. If you lose browsing capability after you remove spyware, running WinSockFix may fix the problem.

• SUPERAntiSpyware Reputable, pretty effective, and removes spyware for free. Real-time protection is available if you buy a license.

• HijackThis If you have stubborn malware, HijackThis may be able to uproot it. It's recommended that you get expert help to interpret the HJT log output.

• SpywareBlaster from JavaCool Software An immunization tool.

• Spybot Search & Destroy 1.4, a freeware classic with some immunization capabilities.

• Windows Defender Defender is free to Windows XP users, and is included in Windows Vista. It does provide real-time protection. To be blunt, I have not been impressed with Defender.

Downloadable security utilities

• McAfee Stinger is a limited-scope remover for about 50 common types of malware.

• F-Secure BlackLight Beta is a specialized rootkit detector/cleaner, currently in beta testing.

• Panda AntiRootkit is another rootkit detection/removal utility.

• GMER is yet another reputable rootkit detection/removal utility.

• Microsoft Baseline Security Analyzer checks for a wide range of Microsoft security issues.

  Below: Microsoft Baseline Security Analyzer 1.2.1, a free tool. Click for a full-size image.