An credential verification service (CVS) authenticates digital credentials, such as, digital certificates, at the request of online service providers. The CVS stores the authentication results and transaction information in a central activity log. The transaction information can include a size of the transaction, the online service requesting the authentication, an internet protocol (IP) address of a computing device originating the transaction and the goods or services involved in the transaction. The CVS generates an activity report from the activity log that lists the authentication results and the transaction information. A fraud detection module within the CVS analyzes the activity log to identify any unusual patterns in order to identify fraudulent activities or general misuse of the digital credential.