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APT28 deploys NotDoor backdoor via Microsoft Outlook

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📰 2 unique sources, 2 articles

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APT28, a Russian state-sponsored threat group, has been using a new backdoor malware called NotDoor to target Microsoft Outlook. The malware exploits Outlook as a covert communication, data exfiltration, and malware delivery channel. NotDoor is a VBA macro that monitors incoming emails for specific trigger words. When triggered, it allows attackers to exfiltrate data, upload files, and execute commands on the victim's computer. The malware is delivered via a legitimate signed binary, Microsoft's OneDrive.exe, vulnerable to DLL sideloading. The backdoor was identified by researchers from Lab52, the threat intelligence arm of Spanish cybersecurity firm S2 Grupo. The malware has been deployed against companies in NATO member countries, using advanced techniques to evade detection and maintain persistence. NotDoor supports multiple commands for data exfiltration and file uploads, and uses Base64-encoded PowerShell commands for various operations. The malware creates a staging folder in the %TEMP% directory to store and exfiltrate files, encoding them with custom encryption before sending via email. APT28's attacks involve the abuse of Microsoft Dev Tunnels for C2 infrastructure, providing stealth and rapid infrastructure rotation. The attack chain includes the use of bogus Cloudflare Workers domains to distribute additional payloads, demonstrating a high level of specialized design and obfuscation.

Timeline

  1. 04.09.2025 21:10 📰 1 articles

    NotDoor targets NATO countries with advanced evasion techniques

    APT28 has been deploying NotDoor against companies in NATO member countries. The malware uses advanced techniques to evade detection and maintain persistence. NotDoor supports multiple commands for data exfiltration and file uploads, and uses Base64-encoded PowerShell commands for various operations. The malware creates a staging folder in the %TEMP% directory to store and exfiltrate files, encoding them with custom encryption before sending via email. APT28's attacks involve the abuse of Microsoft Dev Tunnels for C2 infrastructure, providing stealth and rapid infrastructure rotation. The attack chain includes the use of bogus Cloudflare Workers domains to distribute additional payloads, demonstrating a high level of specialized design and obfuscation.

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  2. 03.09.2025 23:49 📰 1 articles

    APT28 deploys NotDoor backdoor via Microsoft Outlook

    APT28 has been using a new backdoor malware called NotDoor to target Microsoft Outlook. The malware exploits Outlook as a covert communication, data exfiltration, and malware delivery channel. NotDoor is a VBA macro that monitors incoming emails for specific trigger words, allowing attackers to exfiltrate data, upload files, and execute commands on the victim's computer. The malware is delivered via a legitimate signed binary, Microsoft's OneDrive.exe, vulnerable to DLL sideloading. Lab52 researchers identified NotDoor and attributed it to APT28.

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