See 4.3.13 for a description of this threat.

OPC UA Client and Server applications counter Repudiation by the signing of Messages that are specified in OPC 10000-4. A signed message indicates that the message originated from the owner of the private key. During OpenSecureChannel and Session establishment the communicating parties are clearly identified and confirmed. Lastly Auditing as described in OPC 10000-4 will track the information associated with the message.