Game guard is an anti-cheating application used with MMORPGs . I have read that such applications acts as rootkit over the pc. How dangerous it is to play MMORPGs that uses this application? How could it be exploited (either by the company it self or by a malicious hacker) who hacks into the pc or the main company?
When you accept to run software from anyone, including the game itself, you are already trusting that software. If the software publishers are intent on attacking your PC, then they can do it from the main game binary; they don't need to use Game Guard for that. As a corollary, refusing to run Game Guard will not protect you from that company.
One case could be made that Game Guard, being used by many games, becomes a higher-value target: successfully planting a backdoor in Game Guard would give access to a lot more machines than a backdoor in just one game. In that respect, Game Guard comes close to operating systems.
How dangerous Windows is ? (or Linux, or MacOS X,...)
The terms root kit etc have specific meanings in the security world, and it doesn't necessarily mean the program is malicious, simply that it's hiding files on the system. Don't get me wrong - I wouldn't like to have this crap on my computer, but I'm just trying to clarify scary words.
Given the amount of information Game guard does, or supposedly does, gather about your computer you would certainly be placing a lot of trust in their company. With supposed keyloggers built in (haven't seen verified proof only speculation) it gets very dodgy, and I think it's a huge breach of privacy to simply protect against game cheating.
In terms of vulnerabilities it's the same as any software on the market, if bugs are found they could be exploited, leading to control over the computer.
Summary - I personally wouldn't enjoy having it on my computer, I think it has a lot of questionable practices, security wise it's not much different to any other software, and whether or not you should use it comes down to how you feel about what it does.
GameGuard acts as type of inter-process communication proxy, it can stop applications, hide process information from the user, and I believe also has a key-logger.
This is about as nice as Sony's CD Rootkit from a couple of years ago.
This is pretty nefarious because you are already giving the application a lot of control, equivalent to a remote shell in many regards. So if their monitoring network or control points were compromised, this could be pretty awful.
I do not use any games with the technology, but I wonder if you can protect yourself using sanboxing or a virtual machine, or if the technology blocks those attempts to limit its control. At the same time, to the average user this is probably the same tradeoff as giving Facebook the minute-by-minute details of your life.
I wonder if anyone has done a study looking at the network traffic it sends back to see if its at least encrypted or if its not, what content or intercepts are possible.