A condition on a client that is communicating with a server is determined by issuing a challenge to the client, causing the client to produce a response indicative of the condition. The server compares the response to an expected response to determine if the condition is as expected, and if not, takes appropriate action, such as terminating the connection with the client. The challenge preferably includes parameters and a code segment that causes the client to produce the response by executing the code segment. The code segment could perform a one-way hashing algorithm of a portion of memory indicated in the parameters. The server can thus determine if the client is using a modified basic input output system, modified software, pirated software, or whether other conditions exist on the client. The challenge can be changed to prevent the client from returning a false, predetermined response to the challenge.