Web proxy app becomes Bitcoin mining trojan

If your PC is running a little hotter than usual, there’s a chance it’s running a Bitcoin miner secretly installed via a web proxy app that researchers are classifying as a “potentially unwanted program” (PUP).

PUPs tread the grey area between legitimate software and malware. A recent example was Yontoo for Mac OS X, a browser plugin from a legitimate company that supposedly enhanced the browsing experience for users. The catch was that it also installed adware that presented ads on affected Macs that wouldn’t have otherwise been there. Meanwhile, Yontoo LLC secured commissions from affiliate ad network programs.

A new PUP does basically the same thing, but instead of plugging the affected PC into an affiliate advertising network, it’s installing a Bitcoin miner in the hope of using other people’s hardware to earn a portion of the currency that last week traded for over $1,000 a unit.

Discovered by researchers at security vendor Malware Bytes, the offending software is a web proxy called YourFreeProxy from a company known as We Build Toolbars (WBT) LLC or its other name Mutual Public.

The proxy uses an installer called monitor.exe, which installs among other things a popular Bitcoin miner “jhProtominer” that’s available on open source code repository Github.

Like any self-respecting vendor of PUPs, WBT was careful to ensure that whoever installed its proxy had agreed to the company’s end-user license agreement. As noted by Malware Bytes’ lead researcher, Adam Kujawa, the notification that a Bitcoin miner would be installed came in the form of:

**COMPUTER CALCULATIONS, SECURITY: as part of downloading a Mutual Public, your computer may do mathematical calculations for our affiliated networks to confirm transactions and increase security. Any rewards or fees collected by WBT or our affiliates are the sole property of WBT and our affiliates.**

“Their explanation is basically the purpose of Bitcoin Miners and that they will install this software on the system, run it, use up your system resources and finally keep all rewards from the effort YOUR system puts in. Talk about sneaky,” Kujawa wrote in a blog post.

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