I want answers from people who know what they are talking about.
There's no doubt that magnets would wipe old, unshielded magnetic discs. However, new modern magnetic drives are shielded and we have solid-state memory.
A sufficiently strong magnet, held sufficiently close, for a sufficiently long time can and will destroy data on a hard drive.
The conflicting true versus false claims you have heard are almost certainly based on an arbitrary definition of "sufficient".
On the other hand, I don't know if a magnet could do any damage to the computer system itself, except inasmuch as it could destroy the boot data stored on the hard drive, rendering the computer unbootable until a new system is installed.
Well they can definitly destroy CRT monitors as well. I did it by semi-accident as a child once (my parents were not amused).
In order to destroy modern hard drives, magnetic field in the range of Tesla is required. Such a magnitude of magnetic field can be generated by powerful neodymium magnets, metallic scrap picking machine's electromagnet, MRI machine etc. Damage to entire computer can occur only by powerful electromagnet pulses which can create high voltage transients (of the order mega volts and mega amperes) sufficient enough to melt the p-n junction of the semi-conductors.
I was considering the box/CPU only.
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