BTER Hack

On February 14, 2015, 7,170 BTC, worth about $1.75 million at the time, was taken from the cold wallet of BTER, a China-based exchange, in a single transaction (f5b0363f03e1ed8bb812c135361ea93590c831ce9f13a3750be1b93575baccc6). BTER announced the loss the next day, shut down its platform, said withdrawals of user balances would be arranged later, and said on Weibo that it was working with law enforcement. It offered a 720 BTC bounty for help recovering the coins.

BTER did not explain how the cold wallet was compromised. Later accounts say the so-called cold wallet was not kept offline and was protected by a single key rather than multi-signature. The stolen coins were split across several wallets, and BTER said it traced them to the Bitcoin Fog mixer without recovering them.

On March 10, 2015, BTER said users would be compensated in full, paying in batches from trading fee income and an interest-free loan of 1,000 BTC from Jua.com, and began reopening services. This was BTER's second major loss in about six months, after an August 2014 theft of about 50 million NXT.