A METHOD FOR PROTECTION COMPUTER MEMORY AGAINST UNAUTHORIZED ACCESS includes partitioning data received via communication links and instructions for controlling the processing of data incoming from a protected computer by means of an external controller. To substantially eliminate any breach in the firewall all the messages received in a communication session are logged into an external storage locked at the side of the protected computer, the external storage input is locked, and independently of CPU, long-term storage and operating storage of the protected computer, messages are sorted into textual and/or iconic files, program files and files of undefined type, and the demand in the files received and admissibility of their usage in the protected computer is individually determined.A DEVICE FOR CARRYING OUT THE METHOD comprises an external storage, a controllable input switch and a controllable output switch connected to the external controller.