Revert "Update Stealc.yar"

[kevoreilly]

Reverts #2674

[gemini-code-assist]

Summary of Changes

Hello @kevoreilly, 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 reverts a previous update to the Stealc.yar YARA rule. The primary purpose is to remove the dependency on the pe module and specific import checks (tier0.dll and msdart.dll) from the Stealc rule's condition, effectively simplifying the rule and making it less restrictive regarding PE imports.

Highlights

• YARA Rule Modification: The Stealc YARA rule has been modified to remove the import "pe" statement and the condition not (pe.imports("tier0.dll") or pe.imports("msdart.dll")). This simplifies the rule's logic by removing checks for specific PE imports.

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[gemini-code-assist]

Code Review

This pull request reverts a previous change to the Stealc.yar YARA rule. The revert removes the dependency on the pe module and a condition checking for specific DLL imports. This simplifies the rule and makes it consistent with the StealcV2 rule in the same file. The change appears correct and likely addresses issues introduced by the reverted commit. I have added one suggestion to improve the rule's condition to enhance performance and reduce potential false positives, which aligns with the likely intent of the original change.

[gemini-code-assist]

While reverting the pe.imports check is likely necessary, the rule could be made more efficient and less prone to false positives on very large files by adding a filesize check. This is a common practice in YARA rules to constrain their scope and improve performance.

        uint16(0) == 0x5A4D and filesize < 1000KB and any of them