Once again there was another double spend attempt on the exchange. The exchange closed block chain processing when it happened. As a result of these continued attacks I've had to close the exchange. As it says from the main page:
Deposits for I0Coin and Bitcoin have been suspended, along with trading. Due to low network power of the I0Coin chain over the last couple of weeks there have been attempts to do 51% double spend attacks. The exchange would stop processing the block chain when these were detected and users will have noticed this, as deposits/withdrawals were suspended while I investigate. I'd then re-open with a higher deposit confirmation limit.
Some of the double spends were successful and a total of 198 bitcoins were successfully taken from the exchange. This involved anonymous users operating over TOR depositing I0Coins, trading for bitcoins, withdrawing the bitcoins and reversing the original deposit.
Due to this loss and the risk involved in continuing to operating an exchange for a chain which has, or can easily get, an attacker with >51% of the power, I've closed the exchange. Please withdraw all bitcoins and I0Coins before 31 Oct 2011 12:00 UTC. You can reach the exchange operator at
admin@bitparking.com if you have any questions. It's unfortunate that the actions of a few have to stop the exchange usage for many honest users.
The basic approach from the attacking user was to deposit about 120,000 I0Coins, sell them, withdraw the BTC then invalidate/remove the original deposit. All the successful attacks (totaling 198 bitcoins or so) were done by a user operating over TOR. The user used accounts with names like:
* youdozeek
* mooncoin
* ploti
* adolf
* mojimcheo
The bitcoin addresses that were withdraw too were:
* 13kf6BR32STEuW7FSKVbM3WNUcF6nqcP3q
* 1H3Zx5a7fTWnpt8pfZnwekQzQYb4497vWb
* 1AKxgg8jESUvooeHtNvaSQYhbPCyv7wYZF
* 1G8XACmUXoTF3FaA5bATSD3fnSR2WQXVJH
* 1PoUHcuTqoSiKupYzkQUbPHE4SwTPBT9Ht
If you were one of these users and don't believe you did a deliberate double spend, please get in touch.