A method for authenticating a user identity asserted from a client device may include receiving information that asserts a user identity including a user identifier, accessing external data stores to receive data rows that are associated with the user identity, and accessing monitoring systems to receive data vectors. The monitoring systems may monitor transmissions to receiving systems, the data vectors may include numerical target values for the receiving systems, and the data vectors may be accessed using the user identifier. The method may also include determining whether the data rows can be matched to the data vectors, and based on that determination, authenticating the user identity.