How to check a download for a virus

From Google Operating System
If you get a file from a site you don't know very well (like a game or a screensaver), the first thing you should do is scan it using an antivirus. The problem is that your antivirus might not be very good or might not include the signature of the trojan included in the file you've just downloaded. So a good idea is to have a second opinion, but you can't install more than one antivirus (unless you disable the real-time protection).

VirusTotal is a site where you can upload a file smaller than 10 MB and it will be scanned by a large number of antivirus software (the current number is 31), including: Kaspersky, BitDefender, F-Secure, Panda. The file will not be scanned instantly, but you'll have to wait a short time (usually around one minute), depending on site's load. You'll get a report like:


If you see conflicting responses, look at the most trustworthy engines (some tests) and at the number of engines that report a virus. In the situation depicted in the screenshot, I can safely assume that the file is clean.

The service is available by email too: send a mail to scan@virustotal.com with the subject SCAN. If you use Gmail, you'll have to rename executable files (for example, from setup.exe to setup.ex1) to be able to send them.

A similar service is Jotti's malware scan, that has a bigger limit for the file size: 15 MB, but uses less antivirus engines.

{ Thank you, Google! }