One wonders whether they wised up and started cryptographically signing all their executables and game assets, having it then not run if the sigs and MD5/SHA512sums do not validate. Certainly with phone-home schemes available via Steam, etc., it is likely they could have a non-local privkey they are verifying against. This would make things very difficult to crack. If people have figured out a way to make complex game binaries have acceptable performance while being comprehensively paranoid about tampering, that'd be one heck of an achievement. Would make modding basically impossible though, so there is that. Fun speculation in any event.