Protector...

Protectors are items sold by the grocery store lady that prevent 'botters',
people who use a hack to auto-hunt units while they sleep, from ruining the
experience of others. They're only 100 gold each, and to prevent abuse on
non-cheating players, can only be used once per hour. You'd better make sure
your target isn't just a taciturn hardcore power levelling fiend, lest you end
up wasting a protector and spending an hour lamenting in sorrow when you see a
real botter.

To use the protector, simply click the botter, open your inventory with the 'I'
button, and right click the protector. This will summon a weak hitting dog in
front of your target, and the application of the bot says there is a hostile
enemy in front of it. The protector explodes when attacked, killing the botter.
Also, you can hook the protector to a hotkey by clicking the item, then clicking
one of the numbers at the bottom center of the screen.
http://www.gamefaqs.com/computer/doswin/file/930711/43300