Well, that depends on what counts as "hard".
From one point of view,
 it's really easy to damage them electrically - just connect straight
 to
 mains power; few RS232 ports will withstand that, even over here
 where
 mains pwoer is only half the voltage it is on your side of the pond.
 But it _is_ true that it's hard for someone not totally boneheaded to
 damage them accidentally.
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 If you are hell-bent on killing something, mains power applied between
 appropriate terminals will usually do the job, even for otherwise robust
 devices such as 2N3055s or big speakers. Unless of course it's a washing
 machine, in which case a hand grenade or dynamite would be more useful.
 Or 10kV from the local substation.
 /Jonas