okay, i meant closed hacking, and yet i named open hacking programs. well, i'm an idiot.....but the oly hacking programs i can think of for closed would be maphack, drop hacks, pindlebot, and color hacks. all of them have a HUGE chance to be infected with viruses and only one of them really matters (drop hack). except, i thought pindlebot was to blame for much of the lag, and the whole "waiting lines for games" bit.
open play is good for trying out new builds and item combos. probably half of the builds that exist today were found by using a hacking program to speed up the process. hell, i've used a couple myself...jamella and shadowmaster, and unwittingly a drop hack, but that was only the demo for d2, which was only singleplayer and only blood moor, cold plains, and burial grounds. bloodraven runs were fun, though.