Someone owns that box. Someone paid for it to be hooked to the net and someone is paying for the bandwidth. There are ways to get these folks' attention; if a process on the box is messing with other boxes, that alone violates the TOS of just about every ISP or colo that I know of... the box can be disconnected and remain so until it gets cleaned up.
OTOH, if you prefer to take the bull by the horns and invade another box and kill some processes, that action just puts you in legal hot water.
Fence it off and complain to the hostmaster and the ISP.