Find and fix the backdoor in the game

Find and fix a "backdoor" vulnerability on the Perfect World game server.

Initial data:

• Only binary files of the server are available.
• There is no source code.

Requirements:

1. Analyze the server binaries to find the vulnerability.
2. Localize and eliminate the potential "backdoor".
3. Test the fixed server to ensure safety and stable operation after the changes are made.

Background:

A critical vulnerability — backdoor — was discovered on the Perfect World game server, through which attackers gained access to the server. As a result of the attack, 3 different VDS were compromised, leading to a complete removal of the operating system and data loss.