@Auris: I did my best to explain the situation in the official Bitmarket thread. If you want more details:
- First hack happened on 5th october. Two accounts were involved then. While it didn't alarm me much (from time to time these kind of things happened because people were careless with their passwords), I did set up a withdrawal hold feature. It worked like this: when you withdrawed more than 5 BTC from your account, it would hold it until I accepted it manually.
- Yesterday (9th october), presumably same hacker struck for the second time. This time, he accessed a bunch more accounts (around 15). Everytime he got something in his fraudulent account (CoonBreakair, jlcducky and probably hellonona) he would withdraw it immediately to his private BTC address. First, he tried to withdraw larger sums of BTC, which were held by the mechanism described above. These were returned to their respective owners. Then he probably noticed what's wrong and began to withdraw smaller sums, like 1-5 BTCs at time, which ultimately allowed him to drain ~182 BTC, until I was alarmed by users and stopped him. I immediately put all withdrawals on hold, even small ones, banned him and then disabled the site. So after that he couldn't do any more damage, but he still managed to withdraw aforementioned 182 BTC to his private BTC address.
I hope this explains it all.
Edit:
there are people, having unique, strong, cryptographically generated passwords, that have not been used anywhere else and still got ripped off.
Few members affected had not-reused passwords, majority acknowledged that they reused their login details elsewere (Mt. Gox, Intersango, among others). So while it's puzzling how passwords of these two members were cracked, it could be just about anything. One of these members has changed his password and few hours later attacker accessed his account again! It looks like a classic trojan/keylogger attack if you ask me.