- Virus: a virus attaches itself to another program and is activated to cause damage when the host program is opened;
- Trojan horse: hides the true identity of user. The damaging behaviour is revealed when the program is activated;
- Logic bomb: triggers actions when conditions occur;
- Time bomb: triggers action when a specific time has elapsed;
- Trapdoor: an electronic hole in software that is left open by accident or intention;
- Worm: a virus that replicates on to other machines through a network;
- Rabbit: replicates itself without limit in order to exhaust a resource;
- Pharming: duping online bank customers into revealing account details.