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Detects a suspicious pattern in RTF files which downloads external resources as seen in CVE-2022-30190 / Follina exploit

yara HIGH signature-base
exploitflorian-roth
This rule was pulled from an open-source repository and enriched with AI. Validate in a test environment before deploying to production.
View original rule at signature-base →
Retrieved: 2026-08-03T23:00:00Z · Confidence: medium

Hunt Hypothesis

This hunt hypothesis targets adversaries leveraging the Follina exploit (CVE-2022-30190) to execute malicious RTF documents that trigger unauthorized external resource downloads via MSRTD.dll. A proactive search in Azure Sentinel is essential because this technique often bypasses traditional email security controls by exploiting a zero-day vulnerability, allowing attackers to establish initial access before standard detection mechanisms engage.

YARA Rule

rule SUSP_Doc_RTF_ExternalResource_May22 {
   meta:
      description = "Detects a suspicious pattern in RTF files which downloads external resources as seen in CVE-2022-30190 / Follina exploitation"
      author = "Tobias Michalski, Christian Burkard"
      date = "2022-05-30"
      modified = "2022-05-31"
      reference = "https://doublepulsar.com/follina-a-microsoft-office-code-execution-vulnerability-1a47fce5629e"
      score = 70
      id = "71bb97e0-ec12-504c-a1f6-25039ac91c86"
   strings:
      $s1 = " LINK htmlfile \"http" ascii
      $s2 = ".html!\" " ascii
   condition:
      uint32be(0) == 0x7B5C7274 and
      filesize < 300KB and
      all of them
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

This rule contains 2 string patterns in its detection logic.

References

False Positive Guidance

Here are 5 specific false positive scenarios for the CVE-2022-30190 / Follina detection rule, including targeted filters and exclusions:

Original source: https://github.com/Neo23x0/signature-base/blob/main/yara/gen_doc_follina.yar