Are these anti-thief systems magnetic? In doubt I didn't bought it.

If so, that would be a very stupid thing to do

No that variant isn't magnetic. Its just a pushbutton under a adhesive pad, if the pushbutton is let go, the alarm sounds.

And that looks like a demo model only so you can read the specs. There should be packaged ones nearby (with alarm tags) that you take to the checkout.

You would need a several times stronger magnet to do anything anyway. That lil dude will do nothing

@Kimmax This isn't removed with a magnet, rather you enter a code on a wall mounted keypad, or disarm with a remote control.

But the OP was talking about magnets on a hard drive. Even if a hard drive is "empty" data-wise (eg: dd if=/dev/null of=/dev/sda), the platters contain servo-information (written at factory so the electronics can position itself) which, if erased by a magnet, will make the drive unuseable.

There are some stupid shops which puts the hard drives in such plastic "locker boxes" which requires a magnet (which is mounted in the checkout) to unlock... like super strong magnet 15 cm near a hard drive... bzzzzzt...

@sebastian I know, what I meant was that I think that little magnet isn't strong enough to harm any data written on the HDD

All hard disk already have rare earth magnets (very strong) inside. I doubt that this small fella could damage HDD

@SystemZ The magnet inside is calibrated so that Lorenz's force strength can be observed. Put a magnet at certain points may alter head sensitivity or if too strong it can polarize entire sectors in a non-reversible way.