mandiant / mandiant/capa-rules

mimikatz.exe_: encrypt data using speck

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false positive
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Description

Function: `0x420A81`

What it does: Massive switch statement processing opcodes (SQLite VM).

Why it matched: The rule matched on a "tight loop" with XOR/Rotate operations. These are present in the SQLite bytecode engine for data manipulation, but it is not the Speck block cipher.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the rule titled “mimikatz.exe_: encrypt data using speck” and inspect the match at function 0x420A81, where a SQLite VM switch statement triggers on XOR/rotate operations. Reproduce the match against the SQLite bytecode engine and verify that the rule no longer identifies this code as Speck while still detecting the intended cipher pattern.

Written by the indexing model from the issue text.

Assessment

Tech stack
sqlite
Domain
reverse-engineering, security
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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