ACR Stealer: Two observed intrusion chains amid increased threat activity

Between late April and mid-June 2026, Microsoft observed heightened ACR Stealer activity targeting enterprise environments through ClickFix social engineering lures. This information-stealing malware, associated with Amatera Stealer rebranding and offered as malware-as-a-service, deployed through two distinct campaigns. The first utilized WebDAV-delivered payloads with Python loaders and blockchain-based command-and-control resolution. The second employed a fileless approach using MSHTA and steganography-concealed payloads within images. Both campaigns harvested browser credentials, authentication tokens, and sensitive documents from compromised systems. Threat actors leveraged obfuscated PowerShell scripts, scheduled task persistence, and in-memory execution techniques to evade detection. Notable tactics included masquerading as legitimate software updates, utilizing Windows DPAPI for credential decryption, and targeting PDF and Microsoft 365 documents. The blockchain dead-drop techni

Jul 17, 2026 · unknown severity · unattributed attribution