Android Apps Hide Crypto-Currency Mining Malware

Security researchers this week warned that malware designed to mine crypto-currencies has been hidden in apps distributed via Google Play as well as in online forums.

Malware known as KageCoin has been hidden inside two apps distributed through Google Play -- Songs and Prized -- which have collectively been downloaded more than a million times by Android users, Trend Micro mobile threat analyst Veo Zhang said Tuesday in a blog post. While the security firm informed Google about the apps, as of Thursday morning they were still available for download via Google Play.

The KageCoin malware was originally discovered in the wild -- not being distributed via Google Play -- in versions of some popular apps, including Football Manager Handheld and TuneIn Radio, that had been repacked to include code from cpuminer, which is a multi-threaded, CPU miner that runs on Android.

That previous version of KageCoin apparently earned its creators "thousands of Dogecoins," Zhang said. But even with a botnet composed of thousands of infected smartphones, the criminals behind this enterprise aren't getting rich quickly: 1,000 of the Dogecoins crypto-currency are worth only 60 cents. "Yes, they can gain money this way, but at a glacial pace," he said.

Those economics might help explain why the version of KageCoin hidden in the Google Play apps has been updated to work with the WafflePool mining pool, which is designed to mine a variety of "altcoins" -- referring to any crypto-currency that isn't Bitcoin. In exchange for every altcoin they mine, however, they receive a payment, in bitcoins.

As far as malware goes, KageCoin isn't the worst parasite on the books, given that it's somewhat resource-savvy. "The mining only occurs when the device is charging, [so] the increased energy usage won't be noticed as much," Zhang said.

But the same can't be said for a malware family known as CoinKrypt, which has been distributed via online forums based in Spain -- although most of the infections appear to be based in France. Notably, one sign of infection by CoinKrypt is that it consumes a vast amount of resources. "[At] a minimum, users affected by this malware will find their phones getting warm and their battery-life massively shortened," said Marc Rogers, principal security researcher at Lookout, in a blog post. Users' mobile phone accounts, of course, may also get drained. "CoinKrypt might suck up your data plan by periodically downloading what is known as a block chain, or a copy of the currency transaction history, which can be several gigabytes in size."

From a programming perspective, as with KageCoin, this malware is far from sophisticated. In this case, however, "lack of complexity is part of what makes it dangerous," Rogers said. Unlike purpose-built crypto-currency-mining software, the malware includes no throttle to protect the software from overtaxing processors or to manage battery life, and it will continue running until the device loses power, as well as "potentially damage hardware by causing it to overheat and even burn out."

CoinKrypt, like KageCoin, doesn't mine for bitcoins, which are worth about $525 each. Instead, it tries to mine Casinocoin, Dogecoin, and Litecoin. (As of Thursday, Litecoin is worth less than $15.)

Why don't smartphone malware authors try to mine bitcoins directly? The answer has to do with the complex calculations that are required to mine crypto-currencies.

"To control the rate at which new digital coins are minted, the software that runs the currency sets a difficulty rate which governs just how much processing power you need to expend in order to solve the blockchain and get new coins," Rogers said. "The difficulty for Bitcoin is so tough right now that a recent mining experiment using 600 quadcore servers was only able to generate 0.4 bitcoins."

That referred to an experiment conducted by iDrive, which explored whether its idle quad-core servers might provide a secondary income stream by mining bitcoins. But the findings weren't good. "It's a waste of time, so any other company thinking about mining with their infrastructure, learn from us," iDrive's Matthew Harvey told Data Center Knowledge. "Don't do it. You need custom machines to effectively mine bitcoins and generate a real ROI."

But might a botnet composed of Android smartphones and tablets successfully mine altcoins? According to Lookout, based on current difficulty rates, it's 1 million times easier to mine Litecoin than Bitcoin, and more than 3.5 million times easier to mine Dogecoin than Bitcoin.

Based on the company's tests, however, today's smartphones simply aren't powerful enough to mine altcoins, either. Notably, running AndLTC mining software on a Nexus 4, researchers found that they could achieve about 8,000 hash calculations per second. But based on the difficulty level set for Litecoin (LTC), that capability "would net us 0.01 LTC after seven days non-stop mining," Rogers said. At today's exchange rates, that haul wouldn't even be worth 20 cents.

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