Symantec researchers concluded that the recently created Thunderstrike 2 Mac worm is a viable threat, but one that should be easily fended off by taking a few simple precautions.

“This vulnerability has the potential to be very dangerous for Mac users," Symantec said in a statement emailed to "However, its infection method is the same as many other attacks, so Mac users can protect themselves by continuing to practice good security hygiene.” 

Thunderstrike 2 targets a Mac's firmware through an attached Thunderbolt accessory like an Ethernet adaptor. The attack is unleashed when the computer is rebooted and the infected accessory can damage any device to which it is connected.

Symantec said its staff has not yet come across this threat in the public domain, but Malwarebytes had found a version of this malware capable of creating a slew of adware applications.