Studying for Security+ and can't find a straight answer. Thanks in advance :)

A short simple answer defined here as well as some other good little tid bits, but if this is for homework I suggest you really get out and do some research. Your teacher probably isn't going to be impressed with a one sentence answer to this. Anyway by gaining the trust of a computer that is trusted by the target network you can bypass alot of security. Have a look here transitive attack.

This is not a homework assignment lol. Thank you for your post! There are new materials in the 2011 Security+ that I couldn't find a solid answer to.