An anonymous reader writes: Apple has shut down what appears to have been the first, fully-functional ransomware targeting Mac computers. This particular form of cyber threat involves malware that encrypts the data on your personal computer so you can no longer access it. Afterwards, the hackers request that you pay them in a hard-to-trace digital currency — in this case, bitcoin — in order for you to retrieve your files. This ransomware, called KeRanger, was first reported by researchers at Palo Alto Networks. They also noted that Apple has now revoked the abused certificate that was used in the attack and updated its built-in anti-malware system XProtect with a new signature to protect customers.