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I am analyzing a malware at the moment which scans for a lot of filenames and ClassNames to recognize if it is under supervision or not.

My problem is, that all the filenames and ClassNames are stored as Hashes. Therefore i did some kind of dictionary attack (with a list of tools I know). It was very effective - but out of 20 hashes, i am still missing one!

I am searching for days now... it drives me crazy :D

As you can see, there are some tools missing in my list - can you complete it? Please think of your most favourite tools and take a look at the list - are they already in there? :)

Thank you very much in advance!

In case you need a list like this one day, feel free to use it.

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  • If your current tools worked for 95%, chances are that that word is just not in your dictionary. – Jongware Feb 13 '18 at 18:32
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    I added every tool to the list I ever used, then i looked up the ClassName of each and hashed it using the Algorithm above. Finally I compared the hashes to the list of hashes i extracted from the malware. Therefore yes, this last tool it is not in the list - that's exactly the problem since I do not know any more RE tools for Windows. – flood Feb 13 '18 at 19:02
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I would try a Z3 solver if simple bruteforcing fails. The hashing function doesn't seem that hard at the first glance. Of course there aren't any pre-made tools (I think) and a minimal use of your gray matter is required.

https://www.google.com.au/search?q=z3+solver+hash

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  • You can find a lot of material about using Z3 for reverse-engineering here: Yurichev's Blog. Quite interesting tool, indeed. – perror Feb 14 '18 at 8:41
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    Vitaly, the problem is that Z3 might find whatever that creates that hash. I really doubt that the hash is cryptographically safe, thus, there will be a gazillion or more collisions. – joxeankoret Feb 14 '18 at 9:06
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    thanks! but yes, i had around 3000 collisions per hash within the first 12 hours of brute-forcing. anyway, thank you for the hint! – flood Feb 14 '18 at 15:07
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    @joxeankoret I do not see a problem in collisions - find your gazillion and filter out the only (hopefully) valid one via some simple tool that checks for valid names. Extremely easy in Windows with blah.exe/dll/… name structure, and in Unices just look for alphanumeric space. This is a basic approach in "cryptanalysis". OP if you already have your collisions, then you're already half done, not need for Z3. – Vitaly Osipov Feb 23 '18 at 8:15

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