Malware Has a New Way to Hide on Your Mac

Malware on Apple's MacBook and iMac lines is more prevalent than some users realize; it can even hide in Apple's curated Mac App Store. But the relatively strong defenses of macOS make it challenging for malware authors to persist long-term on Apple computers, even if they can get an initial foothold. Additionally, the avenues available for lurking on macOS are so well known at this point that technicians and malware scanners can flag them quickly. That's why more subtle approaches are significant.

At the Virus Bulletin security conference in Montreal on Wednesday, Mac security researcher Thomas Reed is presenting one such potentially dangerous opening. When you launch an app installer in macOS, a program called Gatekeeper checks to see whether the app originated from the Mac App Store, or is cryptographically signed by a developer who has registered with Apple. All legitimate programs have to be "code signed" to establish their validity and integrity. By checking a file's code signature, Gatekeeper can warn you if a program is malware or if someone has tampered with an otherwise benign installer.