System and method for detecting and preventing attacks against a server in a computer network

A computer-implemented method, performed by a substitute server system including one or more servers and memory storing one or more programs for execution by the one or more servers, the method comprising:

• at the substitute server system:
• receiving an access request from a terminal device to a network server distinct from the substitute server system;
• extracting a web page address from the access request and comparing the web page address with cached records stored in the substitute server system;
• determining whether the access request matches a cached record stored in the substitute server system;
• in accordance with a determination that the access request matches a cached record stored at the substitute server system,
• returning the matched cached record to the terminal device;
• in accordance with a determination that the access request does not match a cached record stored at the substitute server system,
• processing the access request for a security check, further including detecting whether the access request includes an illegal access request;
• in accordance with the security check, forwarding the processed access request to the network server;
• receiving a response satisfying the access request, the response including information from the web page, from the network server;
• optimizing the response from the network server;
• and
• forwarding the optimized response to the terminal device.