This means any malicious software on the system can poke a dodgy driver installed by SFV to completely take over the Windows machine. Capcom claims it uses the driver to stop players from hacking the high-def beat 'em up to cheat. Unfortunately, the code is so badly designed, it opens up a full-blown local backdoor.

Let's drill down to the technical details: the capcom.sys kernel-level driver provides an IOCTL service to applications that disables SMEP on the computer, executes code at a given pointer, and then reenables SMEP. In other words, it switches off a crucial security defense in the operating system, then runs whatever instructions are given to it by the application, and then switches the protection back on.

SMEP [PDF] is a feature in modern Intel and AMD x86 processors that, when enabled, prevents kernel-level software from executing code in user-owned memory pages. It's there to stop hackers from tricking the operating system into running malicious software smuggled into an application's virtual memory space – the OS should only be able to run its own trusted code, not anything provided by any old app.

Capcom.sys completely blows this away on Windows: an application simply has to pass control codes 0xAA012044 and 0xAA013044 to the IOCTL, and a pointer to some instructions, and the driver will then jump to that block of code with full kernel permissions.