Avast update mistakenly detects Windows system files as malware

Antivirus software from Avast falsely detects Windows DLL files as dangerous and quarantined them causing users to no longer be able to use some of their applications. The issue is caused by a failed update of the virusscanner that considers various system file as Win32:Kryptik-PFA.


Users on the Avast forum report that the Avast File System Shield feature quarantines Windows system files which causes software like TeamViewer to no longer function.

Avast has confirmed that the the issue is caused by a failed signature update. Users affected are those running Avast version 8 or earlier, the latest version of Avast is 10. The company recommends affected users to update their signature file. Another possibility is to disable the File System Shield temporarily.