Mac owners who use the open source Transmission BitTorrent client are being warned that a version of the installer was distributed via the app's official website, infected with a new family of ransomware.
It is believed that hackers managed to compromise the installer of Transmission version 2.90 on its download site on Friday, March 4, in order to spread ransomware that researchers at Palo Alto Research have dubbed "KeRanger."
The outcome is that if you were unfortunate enough to install Transmission 2.90 onto your Mac, your computer may now be the digital equivalent of ticking time bomb. Because KeRanger waits three days before awaking, encrypting your documents and data files, contacting its command-and-control servers, and demanding a one bitcoin (approximately $400) ransom be paid for your data's safe return.
According to the researchers, the KeRanger malware also attempts to encrypt Time Machine backup files, no doubt in an attempt to make it harder for victims to recover their precious data without paying the extortionists.
And don't imagine that OS X's built-in Gatekeeper protection would have saved you, as it appears that the poisoned KeRanger app was signed with a valid Mac app development certificate.
A message on the official Transmission website confirms the threat to users, and advises that they "immediately upgrade" to version 2.92: