FrostyNeighbor / Ghostwriter (UNC1151, Belarus state-aligned): ESET documents March–May 2026 campaign targeting Polish, Lithuanian, and Ukrainian government and industrial sectors

ESET published a new technical report on 2026-05-14 documenting fresh operational activity from FrostyNeighbor — a cluster ESET and Mandiant track as Ghostwriter / UNC1151 / UAC-0057, assessed as apparently Belarus state-aligned — against Polish, Lithuanian, and Ukrainian government and industrial organisations across a March–May 2026 wave (ESET WeLiveSecurity, 2026-05-14). The Ukraine strand distributes RAR archives via spear-phishing PDFs impersonating Ukrtelecom; the archives drop a JavaScript downloader (a PicassoLoader variant) that fingerprints the victim environment (username, process list, OS version) and beacons every 10 minutes to operator infrastructure. A server-side geofencing check delivers a benign decoy to IPs outside Ukraine, making emulation from a non-Ukrainian network appear clean. Polish and Lithuanian targeting covers industrial/manufacturing, healthcare and pharmaceuticals, logistics, and government organisations — ESET documents victimology spanning both NATO member states in the same campaign wave. Once operators manually approve a victim, a Cobalt Strike Beacon payload is staged, indicating deliberate victim-vetting prior to full post-compromise operations. MITRE ATT&CK: T1566.001 (Spearphishing Attachment), T1027 (Obfuscated Files), T1059.007 (JavaScript), T1082 (System Information Discovery — victim-vetting step), T1105 (Ingress Tool Transfer — Cobalt Strike staging). Detection: alert on JavaScript execution from browser/document-viewer parent-process trees, followed by 10-minute periodic outbound HTTP(S) beacons to a new destination; test detections with Ukrainian-egress routing to bypass the geofencing blind spot.