Description

A new variant of the MacSync information-stealing malware has been observed using a novel delivery method that allows it to bypass macOS Gatekeeper protections by packaging the malicious dropper as a code-signed and notarized Swift application. This evolution removes the need for manual Terminal execution and makes the malware appear legitimate to macOS users and automated security checks. Researchers at Jamf Threat Labs identified the latest MacSync dropper inside a disk image named zk-call-messenger-installer-3.9.2-lts[.]dmg, masquerading as a legitimate installer and served from an external download site. The Mach-O binary within is both code-signed and notarized with an Apple Developer Team ID (GNJLS3UYZ4), allowing it to initially evade Gatekeeper warnings designed to block untrusted software. Once executed, the dropper decodes an embedded payload and retrieves additional malware components from remote servers. To avoid analysis environments, it inflates the DMG with decoy PDFs, wipes execution scripts post-use, and performs internet connectivity and timing checks before running its malicious logic. This technique marks a departure from earlier MacSync variants that relied on ClickFix or manual Terminal command vectors, instead leveraging Apple’s own notarization process to appear trustworthy. Following disclosure, Apple revoked the associated certificate, but the attack highlights how notarized applications can still be abused to deliver threats.