Additions and changes

[bartblaze]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @bartblaze, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly expands detection capabilities by introducing new YARA rules for specific malware and tools, and refines an existing rule for better accuracy. It updates a critical external data feed to ensure continued relevance and improves its data processing. Furthermore, it enhances several existing behavioral signatures with broader coverage and corrects minor issues. A key addition is the introduction of new signatures targeting suspicious Microsoft Management Console (MMC) activities and the setx utility, bolstering evasion detection. The severity of some evasion-related signatures has also been adjusted to better reflect their observed impact.

Highlights

• New YARA Rules Added: Two new YARA rules have been introduced: GrimResource to identify GrimResource malware and its variants, and Rclone to detect the Rclone tool often used for data exfiltration.
• Existing YARA Rule Updated: The RoyalRoad_RTF YARA rule has been updated to refine its description from 'Chinese APT groups' to 'China-nexus APT groups' and adjusted its TLP from 'White' to 'Clear'.
• Abuse.ch SSL Feed Update: The AbuseCH_SSL feed in bad_ssl_certs.py has been updated to use a new download URL and includes revised parsing logic to correctly extract SHA1 hashes and reasons from the new CSV format, ensuring data deduplication.
• Signature Enhancements and Fixes: Several existing signatures have been improved: SuspiciousBrowserDump now includes vivaldi.exe for broader detection, ArchiveWrite now covers 7z.exe and 7zg.exe, and minor description typos were corrected across multiple signatures.
• New Microsoft Management Console (MMC) Signatures: Two new signatures, MMCDotNetLoad and MMCDLLScriptLoad, have been added to detect suspicious activities involving MMC loading .NET assemblies or various scripting engine DLLs, enhancing evasion detection.
• Severity Adjustments for Evasion Signatures: The severity of UsesMSProtocol, UsesWindowsUtilitiesEsentutl, and UsesWindowsUtilitiesXcopy signatures has been reduced from 3 to 2, reflecting a re-evaluation of their impact.
• New Windows Utility Signature: A new signature, UsesWindowsUtilitiesSetx, has been added to detect the use of the setx utility, which can be leveraged to set environment variables for malicious purposes.

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[gemini-code-assist]

Code Review

This pull request introduces several additions and updates. Two new YARA rules for GrimResource and Rclone are added, and one for RoyalRoad_RTF is updated. The feed processor for abuse.ch SSL certificates is updated to a new URL and parsing logic. Several existing signatures have been updated with typo fixes, grammatical improvements, and expanded detection capabilities. Two new signatures for mmc.exe abuse are added in a new file, and a new signature for setx.exe is added to windows_utilities.py.

My review has identified a critical issue in the new UsesWindowsUtilitiesSetx signature where a copy-paste error resulted in an incorrect signature name. I've also provided suggestions to improve the new Rclone YARA rule and the new MMCDLLScriptLoad signature for better readability and maintainability. The other changes look good.