Restricting access to content based on a posterior probability that a terminal signature was received from a previously unseen computer terminal

A content server comprising:

• a network interface circuit configured to communicate with computer terminals;
• a processor circuit coupled to the network interface;
• and
• a memory circuit coupled to the processor circuit and storing program code which when executed by the processor causes the processor to perform operations comprising:
• maintaining in the memory circuit a historical repository of terminal signature tuples received from a plurality of the computer terminals, each of the terminal signature tuples containing a terminal identifier for a computer terminal and a terminal signature characterizing a measured operation by the computer terminal;
• receiving an access request message through the network interface circuit from a source computer terminal, the access request message containing a terminal signature tuple, the terminal signature tuple in the access request message containing a terminal identifier for the source computer terminal and a terminal signature characterizing a measured operation by the source computer terminal;
• generating a posterior probability value based on processing a combination of the terminal signature tuple contained in the access request message and the terminal signature tuples contained in the historical repository;
• and
• controlling whether access is granted for the access request message to access a resource controlled by the content server based on the posterior probability value.