Besides viruses, what are other types of destructive programs are there?

Trojan Horses -- Like its namesake, this type of program enters a system through an innocent manner and waits for the right moment to unleash its attack.
Worms -- A self-replicating program which exists independent of other programs.
Logic bombs -- A destructive program which is triggered by a date, time, or event, and when triggered, it destroys data and/or other programs.
Salamis -- A special program which invades a financial program and removes assets a "slice at a time", hence the name.
Trap Doors -- These are facilities which permit a hacker to surreptitiously enter a system by means of a security loophole which is either inherent in the operating system, or possibly one which the hacker creates which he is a user on the system.
Session Hacking -- A special type of hacking which requires hardware, software, and communications expertise. It involves the penetration of a system via network lines and/or possibly through the detection of electronic emissions which radiate from active monitors and terminals.