(Reuters) - Cyber criminals have infected hundreds of thousands of computers with a virus called "Pony" to steal bitcoins and other digital currencies, in the most ambitious cyber attack on virtual money uncovered so far, according to security firm Trustwave. Trustwave said on Monday that it has found evidence that the operators of a cybercrime ring known as the Pony botnet have stolen some 85 virtual "wallets" that contained bitcoins and other types of digital currencies. The firm said it did not know how much digital currency was contained in the wallets.