MacOS – Can seller lock/erase the second-hand Mac with Find My Mac

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I recently purchased a MacBook. It's a model that supports Apple's latest OS (at this time 10.9), meaning that it also supports Find My Mac and such.

I'd like to know what I would need to do to ensure the person I bought the system from can't suddenly lock it with a pin/code. (I've seen a few instances of this happening where sellers try ransoming the buyer for more money.)

Here's what I know about Find my Mac and my own guess at a solution—any feedback/advice is appreciated. I don't want to become a victim of having the system I bought locked because the seller wants to try make more money or anything like that. I dont care too much for FMM anyway, and so just want to have it, and its functions off at all times.

Find my Mac does as it says on the tin, it finds your Mac! It also provides options to lock and remote wipe the system—that's all I know of it.

Here is my best-guess solution at having FMM disabled and preventing the person I purchased from being able to track or lock the system:

  • Wipe the disk entirely in another system, no recovery HD, nothing. Total wipe.

    In my opinion this would erase any and all iCloud data from previous users and prevent any tracking/locking of the system when the OS is reinstalled and my own iCloud details used. A PRAM zap may also be done as a precaution (Only seen it mentioned once that previous user data is stored there also).

  • After OS reinstalled, opt against enabling location services and Find My Mac functions. and/or delete Recovery HD. Apparently this is required for FMM to function anyway, and I can deal with having an external USB installer to recover with.

Would that be enough to stop the seller being able to track and lock the system?

Best Answer

I can confirm (from second-hand bad experience & first-hand testing) that a complete disk erase & clean reinstall does not disable Find My Mac. You need to also either:

  • Reset the Mac's PRAM (aka NVRAM aka firmware settings). You can do this by holding Command-Option-P-R at startup, and holding them down until the computer has restarted & chimed three times (actually, it's reset by the second chime, but three is traditional).

  • Set up FMM with your iCloud account. Since the Mac can only be FFM'ed with one iCloud account, this'll replace any previous setup.

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