Process Argument Spoofing is a technique used by attackers to hide their true intentions by changing the command line arguments of a process after it has started. This is done by tampering with the Process Environment Block (PEB).

The PEB is a structure in Windows that holds various information about a running process. Within the PEB, there's a specific section called RTL_USER_PROCESS_PARAMETERS. This section contains an attribute named CommandLine, which is structured as a UNICODE_STRING. The CommandLine attribute is crucial because it stores the command line arguments that were used to start the process.

Attackers exploit this by modifying the CommandLine attribute's buffer. When they change the contents of this buffer, the command line arguments that are visible to monitoring tools and security analysts are altered. This means that even if a process was started with malicious intentions, the attackers can overwrite these initial arguments with harmless-looking ones. As a result, the process can appear legitimate to security systems and analysts, and potentially hiding the malicious activity.

The sophistication of Process Argument Spoofing lies in its ability to alter process information after the process has been created and initially inspected by security tools, making it a bit more challenging to detect.