A technique for preventing selected sets of data words from unauthorized transmission out of the secure perimeter of a computer system is disclosed. A set of security rules is applied to an outgoing data message and if one of the set of rules is triggered, at least a portion of the message is transmitted to a central server that is within the secure perimeter, for scanning by another set of security rules. The central server then sends a security command back to the remote device, which executes the security command before transmitting the outgoing message out of the secure perimeter of the computer system.