The article below explains it. ClamXav is a free antivirus program available for all platforms. It found one infected file on my drive immediately. Luckily it wasn’t this virus; just a generic Windows virus attached to an email:
by Killian Bell
Dr Web, a Russian antivirus software specialist, has discovered a new piece of malware that targets computers running Mac OS X and Linux. Named “Wirenet.1,” once installed the software steals all of the passwords you enter into your web browser, mail client, and other apps, and has the ability to log your keystrokes.
One mitigation is to block communication with 18.104.22.168, which is the control server used by the attackers.