MacSync macOS information stealer variant delivered via signed Swift app
Malware Activity
Summary
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A new MacSync malware variant is being delivered through a digitally signed, notarized Swift app disguised as a messaging installer, raising the risk of Gatekeeper bypass on macOS systems. The dropper uses updated fetching and validation steps, and the payload now includes a Go-based agent with remote command-and-control capabilities. The sample was hosted as zk-call-messenger-installer-3.9.2-lts.dmg on zkcall[.]net/download, and Apple revoked the signing certificate after discovery.
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Timeline
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24.12.2025 18:23 2 articles · 6mo ago
MacSync signed Swift dropper discovery
Initial DisclosureResearchers identified a new MacSync macOS information stealer variant delivered through a digitally signed, notarized Swift application masquerading as a messaging app installer to bypass Apple Gatekeeper checks. The sample was distributed as "zk-call-messenger-installer-3.9.2-lts.dmg" from zkcall[.]net/download, used a large 25.5 MB DMG with embedded PDF documents, and prompted users to right-click and open the app. The dropper performed connectivity and execution checks, enforced an execution interval of roughly 3600 seconds, removed quarantine attributes, and fetched an encoded payload with modified curl flags and dynamic variables. The decoded payload corresponded to MacSync, a rebranded version of Mac.c that first emerged in April 2025, and Moonlock Lab said the family includes a Go-based agent with remote command-and-control capabilities. Apple revoked the code signing certificate after discovery.
Show sources
- New MacSync macOS Stealer Uses Signed App to Bypass Apple Gatekeeper — thehackernews.com — 24.12.2025 18:23
- New MacSync macOS Stealer Uses Signed App to Bypass Apple Gatekeeper — thehackernews.com — 24.12.2025 18:23