Bitcoin's value has
dropped sharply after one of the largest trading exchanges said there
was a flaw in the virtual currency's underlying software.
MtGox said it had halted transfers to external Bitcoin addresses on Friday after detecting "unusual activity".
It said an investigation had revealed it was possible for
thieves to fool the transaction process so that double the correct
amount of bitcoins would be sent.
Bitcoins fell from $700 (£427) to $540.
The Tokyo-based firm said it was now working with the Bitcoin
core development team to "mitigate this issue", which it said was not
limited to its own Bitcoin-wallet system.
A Bitcoin wallet is the place where Bitcoin addresses - the virtual post-boxes where each bitcoin is stored - are kept.
It added that cash withdrawals and transfers of bitcoins to - rather than from - Bitcoin Wallets were unaffected.
MtGox said in a statement:
"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 resent."
Gavin Andresen, chief scientist at the Bitcoin
Foundation - which oversees and develops the Bitcoin software - denied
the problem was its fault.
"The issues that MtGox has been experiencing are due to an
unfortunate interaction between MtGox's highly customised wallet
software, their customer support procedures, and an obscure (but
long-known) quirk in the way transactions are identified and not due to a
flaw in the Bitcoin protocol," he told the BBC.
Garrick Hileman, from the London School of Economics, who
researches alternative currencies, said it was too early to tell how
serious this was for Bitcoin users.
"It's a reason to be concerned, but it's a little early to
say that there's something fundamentally flawed with Bitcoin software.
Previous problems have been corrected," he said.
"It reflects the immaturity of the software. Bitcoin is still a technology in the process of being developed," he added.
In an apparent clampdown on the use of Bitcoin in Russia, the
Russian prosecutor general's office said it was tightening up
regulations surrounding the use of virtual currencies as they could be
used for money laundering or financing terrorism.
It said that the rouble was the only official currency in Russia and introducing others was illegal.
"Systems for anonymous payments and cyber-currencies that
have gained considerable circulation - including the most well-known,
Bitcoin - are money substitutes and cannot be used by individuals or
legal entities," it said in a statement to Reuters.
Improperly used
The use of Bitcoin for alleged money laundering led to the arrests of two men in the US last week.
The Miami-Dade State Attorney Katherine Fernandez Rundle told
Bloomberg in a statement that the "arrests may be the first state
prosecutions involving the use of Bitcoins in money laundering
operations."
"Bitcoins are neither good nor bad. Buying bitcoins allows
money to be anonymously moved around the world with a click of a
computer mouse. Improperly used, Bitcoins are often seen as a perfect
means of laundering dirty money or for buying and selling illegal goods,
such as drugs or stolen credit card information," she added.
Federal charges have already been brought against the operators of two exchanges for money laundering in the US.
Source : BBC News