VirusTotal is an online service providing free malware scanning for individual files. It is not software installed on the user's computer, so it does not perform system-wide malware scans. The service performs aggregate tests using over 40 different antivirus products. Tests can be run either on the website or through e-mail. The variety of antivirus software used by the website allows a user to check for malware that his/her own antivirus solution may have missed, or to verify false positives. VirusTotal was selected by PC World as one of the best 100 products of 2007.