Verifying transactions using out-of-band devices

A verification server comprising:

• a processor;
• and
• a memory storing instructions that, when executed by the processor, cause the processor to perform operations comprising
• obtaining, from a server computer, a first version of session data that describes a transaction occurring between a client device and the server computer, the first version of the session data representing the session data received by the server computer from the client device during the transaction,
• obtaining, from a user device associated with a user of the client device, a second version of the session data that describes the transaction, the second version of the session data representing the session data sent by the client device to the server computer during the transaction,
• comparing the first version of the session data to the second version of the session data,
• determining if a mismatch exists between the first version of the session data and the second version of the session data, and
• taking an action, in response to determining that the mismatch exists.

A computer storage medium having computer-executable instructions stored thereupon that, when executed by a verification server comprising a processor, cause the processor to perform operations comprising:

• obtaining, from a server computer, a first version of session data that describes a transaction occurring between a client device and the server computer, the first version of the session data representing the session data received by the server computer from the client device during the transaction;
• obtaining, from a user device associated with a user of the client device, a second version of the session data that describes the transaction, the second version of the session data representing the session data sent by the client device to the server computer during the transaction;
• comparing the first version of the session data to the second version of the session data;
• determining if a mismatch exists between the first version of the session data and the second version of the session data;
• and
• taking an action, in response to determining that the mismatch exists.