Clean file mistakenly labelled as malware, legitimate email incorrectly labelled spam
A false positive occurs when anti-malware software erroneously labels a clean file as malware.
False positives can cause considerable problems, particularly when the file in question is important to the operation of a system - if security software blocks access to or deletes a vital component, systems may become unstable or even cease to function altogether. Even when less significant files are mislabelled it can cause difficulties for users, for admins who must spend time ensuring the file is indeed valid, and for manufacturers who may halt production of a product while issues are resolved. The 'no false positives' rule is one of the main requirements for certification in the VB100 test process.
False positives are also encountered in spam filtering, when a piece of legitimate email (ham) is mistakenly labelled as spam. Again, serious consequences can result, for example when an important business document does not reach its intended recipient as a result of being filtered by anti-spam software.