An infusion pump and server computer have improved network access security. The infusion pump has a network interface circuit to provide communications over a network and a processing circuit that generates infusion pump data for transmission to a remote server computer. The processing circuit generates a header portion of a request message having at least one field, hashes the header portion but not payload data using a cryptographic hash function and a cryptographic key to provide a hashed code, and inserts the hashed code into the header portion of the request message. The processing circuit inserts the infusion pump data into a body portion of the request message and transmits the request message to the remote server computer over the communications network.