Is it legal to reverse engineer a closed source application in order to check how secure it is if:

  • the software came preinstalled on the device (i.e. I have not signed an EULA)
  • I have signed an EULA that forbids reverse engineering

I have seen a lot of renowned experts reverse engineer popular software and publish details on their flaws and their inner workings on conferences. Is this legal ? (I am particularly interested in EU law)

1 Answer 1


As you have agreed, by contract, not to reverse engineer the product, technically it would be a "breach of contract" to do so, assuming such terms are enforceable where you live (or wherever the EULA selects as the choice of forum).

  • 1
    No, it would not be — reverse engineering may be specifically allowed by the legislature, which may preempt any terms in the contract to the contrary.
    – cnst
    Jul 14, 2019 at 18:19
  • 5
    "No, it would not be" - you say it may be allowed, which means it might not be, not it would not be. You would have to check that before starting any reverse engineering, and I think it is unlikely for the purpose of "security research" which is in practice indistinguishable from hacking.
    – gnasher729
    Jul 14, 2019 at 19:59
  • 2
    @gnasher729 I am not a legal expert, but as I understand it, hacking your own equipment that you own is generally speaking not a crime.
    – user253751
    Jul 14, 2019 at 21:41
  • @user253751 it may not be a crime, but it's probably a breach of contract. Contrary to the implication in this question, software pre-installed on a device typically does have an EULA, and courts have found such "agreements" enforceable despite a lack of signatures.
    – phoog
    Jul 9, 2020 at 11:37
  • 1
    @phoog (note: different courts have also found them unenforceable, so nobody really seems to know. Especially because you don't see the contract until after you've bought the product)
    – user253751
    Jul 9, 2020 at 13:19

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