Something puzzles me in the history of Bter cold wallet transaction
http://www.walletexplorer.com/wallet/Bter.com-coldThe withdrawals from the cold wallet are all 100 BTC withdrawals with only a few very rare exceptions, all sent to the same hot wallet address. This does very much look like pre-generated pre-signed offline transactions being broadcasted as needed, save for the eventual custom offline transactions. The two transactions that happened at the time where the cold wallet was alledged to be compromised are most certainly pre-generated pre-signed transactions because to top-up 200 BTC, they didn't send a 200 BTC tx but two standard 100 BTC transactions exactly like all other transactions made in the last month.
Now, If that's the case and Bter was indeed broadcasting pre-generated pre-signed offline transactions to top-up the hot wallet, how did the cold wallet get compromised? The only two rational explanations I can see are that the transaction of 7k+ was generated and signed offline, or the private key of the cold wallet was leaked by the cold wallet operator and the balance withdrawn. Either way, looks very much like an insider job and it should be easy to find the culprit as you would expect that only a few select people would have access to the cold wallet given that production staff (actually most likely a script) can top-up by broadcasting pre-generated and pre-signed transactions.
Even more puzzling is the fact that the hot wallet wasn't actually emptied. As of now, it still has a balance of 0.01860446 BTC. Sounds very congruant with other round number withdrawals.