Malware Takes Aim At BitCoins


Attackers are creating the first rudimentary Trojans designed to steal the BitCoin virtual currency from users

Proving that cyber-criminals will steal practically anything, researchers have recently identified malware designed to steal BitCoins.

BitCoins are anonymous decentralised virtual currency commonly used online among people interested in keeping their transactions secret. The digital currency is not tied to any real money, but traded on an electronic exchange to establish its value, Andrew C. Herlands, director of security strategy of Application Security, told eWEEK. BitCoins have generally hovered around $14 to $17 (£9 to £11) per unit.


“I have a stone. We both agree it’s worth a dollar. So, when I give you the stone, we agree you now have a $1,” Herlands said, explaining the theory behind BitCoins.

BitCoins are commonly used for illegal transactions, such as buying drugs online, but that is not the only purpose. During its 50-day spree, the hacker group LulzSec also received donations of BitCoins from supporters, noting that the funds were entirely untraceable. The virtual currency may also be gaining some legitimacy, as Meze Grill, a New York City restaurant, recently started accepting BitCoins.

Now a particular piece of malware is designed to trick user accounts into sending money, via BitCoins, to the thief’s account without the user’s knowledge, Alex Gostev, chief security expert at Kaspersky Lab, wrote on 28 June on the SecureList blog. The account receiving transferred BitCoins was suspended because the server hosting it detected suspicious activity.

The mechanism for spending BitCoins is fairly simple. Users buy BitCoins with real money and keep them in their e-wallet, which is client software installed locally on the computer. When a user wants to give someone some BitCoins, they enter a cryptographic code assigned to the recipient, and the “funds” are transferred from the user’s wallet to another person’s wallet via a peer-to-peer network. No names are required, and BitCoins are like cash: Once gone, it’s gone.

Some BitCoins users get in the business of “mining”, or generating more of the currency to increase the pool of available funds. Understandably, this is intentionally a complex process in order to prevent people from flooding the market with BitCoins and devaluing it. The mining is done with a specific application that runs mathematically intensive operations that require a lot of time and computer processing resources.

Gostev analysed Trojan.NSIS.Miner.a, which was “spreading” among Russian users. The Trojan is a malicious module packaged with the legitimate BitCoin Miner tool. Miner.a installs itself onto the compromised machine and launches the mining tool without the user’s knowledge. After the coins are generated, the idea is to transfer the newly minted coins to the attacker’s wallet.

Stealing e-wallets

“Some cyber-criminals seem to think that it’s more profitable to steal computer resources rather than e-wallets,” Gostev said.

Because the mining was being performed across multiple IP addresses, the server hosting the attacker’s account temporarily suspended it for exhibiting botnet-like tendencies.

Gostev called the scam the attacker’s “very own Klondike”, noting that if the account hadn’t been shut down, it could have been a lucrative operation.

Symantec and F-Secure researchers identified a different malware, called CoinBit, targeting BitCoins only a few days earlier. The CoinBit Trojan is “not very professional-looking”, F-Secure researchers wrote on the company blog on 17 June. A “snatch and grab” malware, it attempts to find the wallet file on the infected computer and transfer it to a Hotmail email address using a Polish SMTP server. Having the wallet file gives the attacker full control of all the funds associated with that wallet.

Symantec’s Stephen Doherty recommended that BitCoin users encrypt their wallets with a strong password to prevent attackers from gaining the wallet’s contents.

Both of these Trojans were fairly rudimentary and easy to shut down, as the cyber-criminals’ information, such as email address or server address, were hard-coded in the source code. Attackers will continue to target BitCoins so long as there’s some money associated with the system.

The first malicious software to target BitCoin was Stealthcoin, which first emerged around April. Like the miner Trojan analysed by Kaspersky, Stealthcoin also used a network of compromised machines to create a covert mining operation. In a separate incident, an unknown criminal allegedly transferred 25,000 BTC, worth approximately $500,000, out of an unsuspecting user’s wallet in the first theft of BitCoins this month.

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