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Comment by jeffmcjunkin | Hacker News Reader

Can confirm. Matching decompilation in particular (where you match the compiler along with your guess at source, compile, then compare assembly, repeating if it doesn't match) is very token-intensive, but it's now very viable: https://news.ycombinator.com/item?id=46080498

Of course LLMs see a lot more source-assembly pairs than even skilled reverse engineers, so this makes sense. Any area where you can get unlimited training data is one we expect to see top-tier performance from LLMs.

(also, hi Thomas!)

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My own experience has been that "ghidra -> ask LLM to reason about ghidra decompilation" is very effective on all but the most highly obfuscated binaries.

Burning tokens by asking the LLM to compile, disassemble, compare assembly, recompile, repeat seems very wasteful and inefficient to me.

LaurieWired did a good episode about that kind of thing https://www.youtube.com/watch?v=u2vQapLAW88

That matches my experience too - LLMs are very capable in "translating" between domains - one of the best experience I've had with LLMs is turning "decompiled" source into "human readable" source. I don't think that "Binary Only" closed-source isn't the defense against this that some people here seem to think it is.

Has anyone used an LLM to deobfuscate compiled Javascript?

Yep. They are good at it.

I've used it for hobby efforts on Electron/React Native (Hermes bytecode) apps and it seems to work reasonably well

yes, but it requires some nudging if you don't want to waste tokens. it will happily grep and sed through massive javascript bundles but if you tell it to first create tooling like babel scripts to format, it will be much quicker.

> but if you tell it to first create tooling like babel scripts to format, it will be much quicker.

Can you expand on this? Is that existing tooling for deminification?

for me it was custom scripts looking for data in minified bundles and refactoring for easier protocol reverse engineering, e.g. https://github.com/echtzeit-solutions/monsgeek-akko-linux/bl...

> Has anyone used an LLM to deobfuscate compiled Javascript?

Seems like a waste of money; wouldn't it be better to extract the AST deterministically, write it out and only then ask an LLM to change those auto-generated symbol names with meaningful names?

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