Many free online virus scanners exist. They should never be the sole threat scan being used, but rather as a second opinion. Some infections are incredibly clever, and can mask themselves from the antivirus your system uses. They can’t mask themselves from online scans.
It is literally impossible for a single antivirus product to detect 100% of threats, though some, including NOD32, come very close. Since it is definitely not recommended to have more than one antivirus product on your computer, using an online scan from time to time can provide peace of mind that your system is indeed virus-free.
Screamable recently did a rundown of what they consider to be the top FREE online virus scanners. They include ESET NOD32 (one of our favorites), F-Secure, Kaspersky, and Panda.
Which online scanning utility do you use, and why? Let us know in the comments, or on Facebook or Twitter!