Plugin?
 

Is there a plugin that will allow me to view say the last 20 pages that a specific member viewed?

hmmm...Not that I am aware of but, would be good to have.
If what you are looking for is to see what members read your post, there is a plugin for that here.

Yeah I know of that one, also considering re-adding that one, but this one is based more around security, because there are a lot of banned members intent on disturbing my community.

Simply change the permissions of the banned group so they can't see anything or create an html page just for them and put this in your header

lol I don't think you get what I mean.

Banned members just create new accounts (Yes I ban them via detections) but some slip through the net.

I want to see what they are viewing to get an understanding of what they are up to.

Just simply watching what they're up to is daft!, what good can it do you?, it'll waste your time keep checking hundreds and hundreds of logs, not to mention the amount of queries and server time to run such a thing, ban them and keep them banned
Have you set:
Admincp>User Registration Options>Allow Multiple Registrations Per User = No?
Admincp>User Registration Options>Require Unique Email Address = Yes?
Admincp>User Banning Options>Allow User to Keep Banned Email Addresses = No?

--------------- Added [DATE]1337547194[/DATE] at [TIME]1337547194[/TIME] ---------------

This is what you want if you want to see who's viewed what https://vborg.vbsupport.ru/showthread.php?t=197487

There are a million proxy servers out there so there is no way to ban someone completely/efficiently as they simply can re-register using a proxy.

That said, a banned user when logging in will see nothing but the banned message.