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Request: Add ImpHash #321

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neu5ron opened this Issue Apr 2, 2019 · 1 comment

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neu5ron commented Apr 2, 2019

I am not sure the level of effort to add Import Address Table(IAT) Hashing (ImpHash) to Zeek, similar to how there is MD5, SHA1, SHA256, etc..
This would be a great feature to add to the pe.log and or files.log(for PEs). I think it would be effective and very useful for a few reasons (and probably more that others could think of):

  1. Additional malware detection via "pivoting" off of the ImpHash. Both for internal to external traffic but also lateral movement (east/west).
    ImpHash is useful (to a decent degree) for clustering. For example different samples may have different md5/sha1/sha256 hashes, but if its a similar malware family then its possible they are using the same ImpHash (due to the malware's functionality). I have seen even some recent APTs hitting the news of big breaches but have the same ImpHash in each (despite completely different targets/campaigns).
  2. Legitimate Microsoft PE's being renamed and transferred (over the wire) during lateral movement. This scenario happens a lot when an actor moves a legitimate Microsoft PE, such as Sysinternals PsExec, but changes the name of the file so as not to appear as "psexec.exe".
    One would say to just use the md5/sha1/sha256 of the file, however with different versioning and "modifications" that would make it a non factor to use. Also, its rare that the IAT changes in legitimate binaries through a few version changes.
    This is especially useful for smb.log!

Thanks for your time!

@neu5ron

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neu5ron commented Apr 2, 2019

Especially since the pe.log already obtains "has_import_table" could possibly make this a if statement somewhere saying if "has_import_table" and a redef for enable imphash -- then perform imphashing and add to log.

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