Nimbus Manticore (UNC1549 / Screening Serpens) — Check Point details MiniFast backdoor, Zoom-task hijacking and SEO-poisoning delivery

UPDATE (originally covered 2026-05-23): Following Unit 42's coverage of UNC1549 / Screening Serpens AppDomainManager hijacking, Check Point Research (published 2026-05-22, widely re-reported this week) adds material technical depth on three February–April 2026 campaign waves keyed to Operation Epic Fury (Check Point Research, 2026-05-22; The Hacker News, 2026-05-26). The IRGC-affiliated actor replaced its MiniJunk family with a new backdoor, MiniFast — a 64-bit DLL with a single CheckForUpdates export and a JSON HTTP C2 using API-style endpoints (/agent/init, /agent/poll, /upload/) and a 14-opcode command set including DLL injection, UAC elevation and scheduled-task persistence.

Two persistence/delivery techniques are new versus the prior coverage: (1) Zoom scheduled-task hijacking (T1053.005) — instead of creating a suspicious new task, the malware watches for the legitimate ZoomUpdateTaskUser-<SID> task and hijacks it; (2) SEO poisoning (T1598.003) via a fake SQL Developer download domain ranked on Bing/DuckDuckGo, alongside T1574.008 AppDomain hijacking via redirected .config files. The loader chain validates parent=svchost.exe before proceeding and abused two SSL.com-issued code-signing certificates (Check Point Research, 2026-05-22). Hunt for ZoomUpdateTaskUser-* task modifications by non-Zoom processes, non-default AppDomainManager values in .NET .config files, and execution from user-writable AppData paths.