Wow. I highly doubt that they were hacked via DKPSystem. For one if you have uses posting their account information for World of Warcraft anywhere on the site that is just not safe. Also and I am guilty of not doing this in every case of things I use but you should never use the same user name and password on multiple systems. My DKPSystem account uses a different user name for every site and none are the same as my Wow account name.
The main reason show over and over is a trojan virus delivering a keylogger to their system. This would also account for it being 2 people in the same house even if they are on different computers due to the exploits in file sharing between pc's.
You should have your users scan their PC's for Viruses. Further everyone who plays an Online game such as WoW should run a top notch anti-virus program and Personal Firewall. Personally I don't consider free-ware as top notch.
Of all the people that I have known who have been hacked (one of which was a nephew) they all got it via virus from a download that pertained to WoW. WoW Movies from youtube and various site. One who thwarted the virus before is dropped the keylogger was pickup by accidentally clicking an add for a Gold Seller on one of the many mod sites. Then of course there is that. Mods. Users need to pay attention to the sites they download from and the contents of the mods. The most common mods containing viruses are those that have TGA (game image files) that present something not included in the standard interface for an icon on a bar or button.
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Six Demon BagJack Burton: Hey, what more can a guy ask for?
Egg Shen: Oh, a six-demon bag!
Jack Burton: Terrific, a six-demon bag. Sensational. What's in it, Egg?
Egg Shen: Wind, fire, all that kind of thing!