Concepts and technologies are disclosed herein for providing a transaction validation service. A device can receive a request to validate a transaction requested by a user device, where the transaction can be performed by an application and where the request to validate the transaction can be obtained with a first hash that is created by the user device. The first hash can include a hash of transaction data that is hashed using data stored on the user device. The device can receive an indication that the transaction has been approved, obtain a second hash of the transaction data that is hashed using the data stored on the user device, and determine, based on the first hash and the second hash, whether the transaction should be allowed or blocked.