MANILA, Philippines – The research center of Palo Alto Networks reported Sunday, March 6, that version 2.90 of the Transmission bittorrent client installer for OS X was infected with ransomware, said to be a first for Apple’s operating system.

Ransomware is a form of malware that encrypts files and folders on your system, with the malware owner demanding money in exchange for your data.

In the case of the Transmission ransomware, called KeRanger, the KeRanger malware had a valid Mac app development certificate, allowing it to bypass Apple’s protections.

Palo Alto Networks added that the ransomware waits 3 days before connecting to its command and control servers over the Tor anonymizer network. It then begins encrypting document and data files on a system and will eventually demand a payment of one bitcoin (around $400) to get back the encrypted files.

Palo Alto Networks reported the issue to Apple and to the Transmission Project, with Apple revoking the abused certificate and updating XProtect antivirus signatures. Transmission Project removed the malicious installers from its website and issued a notice on its site about the affected version.

Users who have directly downloaded Transmission from the official website between March 4 and 5, or have downloaded it earlier or from a third-party website will want to check the link in the first paragraph to learn how to check their computer for the malware. – Rappler.com