A security module on a client detects a signed file at the client and reports signing information identifying a certificate used to sign the file and a file identifier identifying the file to a security server. The security server uses the signing information to determine whether the certificate is compromised. If the certificate is compromised, the security server compares a discovery date of the file with a compromise date of the certificate. The security server generates trust data assigning a trust level to the file responsive to the comparison. The trust data assign a low trust level to the file if the comparison indicates that the file discovery date is after the compromise date and assign a high trust level to the file if the comparison indicates that the file discovery date is not after the compromise date. The security server provides the trust data to the client.