ACR Stealer: Two observed intrusion chains amid increased threat activity
From late April 2026 to mid-June 2026, Microsoft Defender Experts observed increased ACR Stealer activity across customer environments.
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Unpacking the AsyncAPI npm supply chain compromise and import-time payload delivery
Threat actors compromised AsyncAPI packages and weaponized trusted CI/CD workflows to distribute malware through npm. -
GigaWiper: Anatomy of a destructive backdoor assembled from multiple malware
GigaWiper, also tracked as BLUERABBIT, is a destructive backdoor that combines multiple wiping and ransomware-like capabilities into a single operational platform. -
StealC and Amadey: Breaking down infostealers and the cybercrime services that deliver them
On June 24, 2026, Microsoft’s Digital Crimes Unit (DCU) facilitated the takedown, suspension, and blocking of domains that formed the backbone of the StealC and Amadey infrastructure. Retain Microsoft Security Experts
Microsoft Security Experts are now available to strengthen your team with managed security services. Learn how to defend against threats with security experts.
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From package to postinstall payload: Inside the Mastra npm supply chain compromise by Sapphire Sleet
A poisoned npm package infected 140+ projects with a hidden payload. -
AI brands as bait: How threat actors are using the AI hype in social engineering
As threat actors operationalize AI to accelerate attacks, they are also leveraging the wider global interest around AI itself as a social engineering lure. -
The Gentlemen ransomware: Dissecting a self-propagating Go encryptor
Microsoft Threat Intelligence presents a comprehensive analysis of The Gentlemen, a Go-based ransomware deployed by affiliates of Storm-2697 that combines per-file ephemeral key encryption with an aggressive self-propagation module to deploy itself across an entire network using series of simultaneous lateral movement techniques per target. -
Exposing Fox Tempest: A malware-signing service operation
Fox Tempest is a financially motivated threat actor operating a malware‑signing‑as‑a‑service (MSaaS) used by other cybercriminals, including Vanilla Tempest and Storm groups, to more effectively distribute malicious code, including ransomware. Modernize your Security Operations Center with Microsoft Sentinel
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Kazuar: Anatomy of a nation-state botnet
Kazuar, a sophisticated malware family attributed to the Russian state actor Secret Blizzard, has been under constant development for years and continues to evolve in support of espionage-focused operations. -
Undermining the trust boundary: Investigating a stealthy intrusion through third-party compromise
Microsoft Incident Response investigated an attack operated through legitimate and trusted administrative mechanisms to blend seamlessly into routine operations and remain undetected demonstrating that intrusions have increasingly avoided using noisy exploits, obvious malware, or custom tooling, instead leveraging systems that organizations already trust within their environments. -
Breaking the code: Multi-stage ‘code of conduct’ phishing campaign leads to AiTM token compromise
Microsoft Defender Research observed a large-scale credential theft campaign that exemplifies this trend, using code of conduct-themed lures, a multi-step attack chain, and legitimate email services to distribute fully authenticated messages from attacker-controlled domains. -
Email threat landscape: Q1 2026 trends and insights
In early 2026, email threats increased with a rise in credential phishing, QR code phishing, and CAPTCHA-gated campaigns, highlighted by Microsoft’s disruption of the Tycoon2FA phishing platform which led to a 15% volume decrease and shifts in threat actor tactics.
