Defense against parasitic computing is generally extremely difficult. The ability to store data or to cause the other party to perform certain trivial computations is often bound to the fundamental functionality of network protocols. This is a characteristic that we cannot conceive of removing without wiping out the Internet as we know it and introducing a host of new problems more serious than the one remedied.

Protecting a single system against becoming a node for parasitic computing is also fairly difficult, because the number of resources stolen from a system is often a negligible fraction of the idle CPU time and memory and, hence, might easily go unnoticed.

Chances are good that parasitic computing has yet to show its full potential and that the threat—irrelevant or nonexistent for single systems but significant for the net as a whole—is here to stay.