Bitcoin Exchanges continue to suspended operations and three exchanges has already suspended the withdrawals. Due to attack, Bitcoin currency is falling on all exchanges due to intensified attack. The value on MtGox exchange has plunged from $926 on 5 February to $530 on 12 February. A spokeswoman for the Bitcoin Foundation Jinyoung Lee Englund said This is a denial-of-service [DoS] attack. Whoever is doing this is not stealing coins, but is succeeding in preventing some transactions from confirming. It's important to note that DoS attacks do not affect people's bitcoin wallets or funds." The attacker seems to exploit a bug in bitcoin software that manipulate the transaction details when sending bitcoins to bitcoin exchange. The alteration is done in such a way that Bitcoin system fails to correctly confirm the transaction and same bitcoins can be sent again for transaction.
"A bug in the bitcoin software makes it possible for someone to use the bitcoin network to alter transaction details to make it seem like a sending of bitcoins to a bitcoin wallet did not occur when in fact it did occur. Since the transaction appears as if it has not proceeded correctly, the bitcoins may be re-sent." said MtGox in his statement.