Computer Science/Trojan Horse

One method of attacking networks remotely is installing Trojan programs that record keystrokes and other processes without users’ knowledge.  Discuss ways to prevent and what actions need to be taken to prevent Trojan programs from deploying in computer systems.

The points that you will receive will depend on the quality of your post.  Points will be given when:

The source of the idea is clearly stated.
The comment clearly and successfully communicates the topic or issue.
Post clearly answers the question being asked.
Cite your source(s) of information.