Bitcoin | Theft and exchange shutdowns

Bitcoins can be stored in a bitcoin cryptocurrency wallet. Theft of bitcoin has been documented on numerous occasions. At other times, bitcoin exchanges have shut down, taking their clients' bitcoins with them. A Wired study published April 2013 showed that 45 percent of bitcoin exchanges end up closing.

On 19 June 2011, a security breach of the Mt. Gox bitcoin exchange caused the nominal price of a bitcoin to fraudulently drop to one cent on the Mt. Gox exchange, after a hacker used credentials from a Mt. Gox auditor's compromised computer illegally to transfer a large number of bitcoins to himself. They used the exchange's software to sell them all nominally, creating a massive "ask" order at any price. Within minutes, the price reverted to its correct user-traded value. Accounts with the equivalent of more than US$8,750,000 were affected.

In July 2011, the operator of Bitomat, the third-largest bitcoin exchange, announced that he had lost access to his wallet.dat file with about 17,000 bitcoins (roughly equivalent to US$220,000 at that time). He announced that he would sell the service for the missing amount, aiming to use funds from the sale to refund his customers.

In August 2011, MyBitcoin, a now defunct bitcoin transaction processor, declared that it was hacked, which caused it to be shut down, paying 49% on customer deposits, leaving more than 78,000 bitcoins (equivalent to roughly US$800,000 at that time) unaccounted for.

In early August 2012, a lawsuit was filed in San Francisco court against Bitcoinica — a bitcoin trading venue — claiming about US$460,000 from the company. Bitcoinica was hacked twice in 2012, which led to allegations that the venue neglected the safety of customers' money and cheated them out of withdrawal requests.

In late August 2012, an operation titled Bitcoin Savings and Trust was shut down by the owner, leaving around US$5.6 million in bitcoin-based debts; this led to allegations that the operation was a Ponzi scheme. In September 2012, the U.S. Securities and Exchange Commission had reportedly started an investigation on the case.

In September 2012, Bitfloor, a bitcoin exchange, also reported being hacked, with 24,000 bitcoins (worth about US$250,000) stolen. As a result, Bitfloor suspended operations. The same month, Bitfloor resumed operations; its founder said that he reported the theft to FBI, and that he plans to repay the victims, though the time frame for repayment is unclear.

On 3 April 2013, Instawallet, a web-based wallet provider, was hacked, resulting in the theft of over 35,000 bitcoins which were valued at US$129.90 per bitcoin at the time, or nearly $4.6 million in total. As a result, Instawallet suspended operations.

On 11 August 2013, the Bitcoin Foundation announced that a bug in a pseudorandom number generator within the Android operating system had been exploited to steal from wallets generated by Android apps; fixes were provided 13 August 2013.

In October 2013, Inputs.io, an Australian-based bitcoin wallet provider was hacked with a loss of 4100 bitcoins, worth over A$1 million at time of theft. The service was run by the operator TradeFortress. Coinchat, the associated bitcoin chat room, has been taken over by a new admin.

On 26 October 2013, a Hong-Kong based bitcoin trading platform owned by Global Bond Limited (GBL) vanished with 30 million yuan (US$5 million) from 500 investors.

Mt. Gox, the Japan-based exchange that in 2013 handled 70% of all worldwide bitcoin traffic, declared bankruptcy in February 2014, with bitcoins worth about $390 million missing, for unclear reasons. The CEO was eventually arrested and charged with embezzlement.

On 3 March 2014, Flexcoin announced it was closing its doors because of a hack attack that took place the day before. In a statement that once occupied their homepage, they announced on 3 March 2014 that "As Flexcoin does not have the resources, assets, or otherwise to come back from this loss [the hack], we are closing our doors immediately." Users can no longer log into the site.

Chinese cryptocurrency exchange Bter lost $2.1 million in BTC in February 2015.

The Slovenian exchange Bitstamp lost bitcoin worth $5.1 million to a hack in January 2015.

The US-based exchange Cryptsy declared bankruptcy in January 2016, ostensibly because of a 2014 hacking incident; the court-appointed receiver later alleged that Cryptsy's CEO had stolen $3.3 million.

In May 2016, Gatecoin closed temporarily after a breach had caused a loss of about $2 million in cryptocurrency. It subsequently relaunched its exchange in August 2016 and is slowly reimbursing its customers.

In August 2016, hackers stole some $72 million in customer bitcoin from the Hong-Kong-based exchange Bitfinex.

In December 2017, hackers stole 4,700 bitcoins from NiceHash a platform that allowed users to sell hashing power. The value of the stolen bitcoins totaled about $80M.

On December 19, 2017, Yapian, a company that owns the Youbit cryptocurrency exchange in South Korea, filed for bankruptcy following a hack, the second in eight months.