Zombie PC

A zombie computer is an inadequately protected computer that has been infected by a Trojan horse and usually a backdoor too.

Such computers can be remotely controlled by a hacker either to send spam (currently, most spam is sent by zombie computers) or to create denial of service attacks to paralyse a network or server victim. Naturally all this goes on without the knowledge of the PC user.

Huge sums are at stake in this illegal practice.