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How attackers built a RAT on a Windows machine using its own .NET compiler

June 22, 2026 · Heimdal Security · Severity: MEDIUM

In May 2026 an attacker compromised a UK medical practice endpoint without delivering a single malicious file. They used PowerShell and the .NET compiler built into Windows to build a Remcos remote access trojan on the machine itself, so signature antivirus had no known sample to match. The thing that caught it was DNS filtering, […] The post How attackers built a RAT on a Windows machine using its own .NET compiler appeared first on Heimdal Security Blog.

Key Takeaways

  • In May 2026 an attacker compromised a UK medical practice endpoint without delivering a single malicious file.
  • The thing that caught it was DNS filtering, […] The post How attackers built a RAT on a Windows machine using.
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