According to Trustwave, a newish botnet targeting crypto-currencies, called Pony, has been responsible for lifting $US200,000-plus worth of Bitcoins.

Pony first emerged during 2013 and was responsible for lifting a couple of million passwords in December, according to a blog post by McAfee.

According to a Trustwave Spiderlabs post:
Not only did this Pony botnet steal credentials for approximately 700,000 accounts, it’s also more advanced and collected approximately $220,000 (all values in this post will be in U.S. dollars) worth, at time of writing, of virtual currencies such as BitCoin (BTC), LiteCoin (LTC), FeatherCoin (FTC) and 27 others,” write the company's Daniel Chechik and Anat Davidi.

“This instance of Pony compromised 85 wallets, a fairly low number compared to the number of compromised credentials. Despite the small number of wallets compromised, this is one of the larger caches of BitCoin wallets stolen from end-users.”

The botnet went after a long list of cryptocurrencies:
Anoncoin, BBQcoin, Bytecoin, Craftcoin, Devcoin, Digitalcoin, Fastcoin, Feathercoin, Florincoin, Franko, Freicoin, GoldCoin, I0coin, Infinitecoin, Ixcoin, Junkcoin, Litecoin, Luckycoin, Mincoin, Namecoin, NovaCoin, Phoenixcoin, PPCoin, Primecoin, Quarkcoin, Tagcoin, Terracoin, Worldcoin, Yacoin and Zetacoin.

Trustwave points out that most users do not encrypt their wallets.