That's a _really_ tough thing to solve. If your opponent has rooted the box of someone with credentials, they're going to get those credentials. If you want any kind of remote work productivity though, you're going to have to let them access your system from networks you don't control and can't lock down.
It's one thing to lock everyone out if you're Booz Allen, but another if you've got journalists on the ground in Cairo competing with Twitter to break news.
The easiest way is to IP limit any services with user privileges.
IP's can be spoofed though, and then you're severely limiting your ability to work flexibly, which doesn't go well for journalists.
Two Factor Auth is another technique that's really coming into it's own now among web systems, but again not super great if someone loses their smartphone or RSA dongle while running from a gunfight and needs to access the system NOW.
I work on the assumption that any password can be compromised at any time, so the system should be able to lock out and roll back a user's edits ASAP, and content-creating users shouldn't be able to get any code executing on the server. Easier said than done with most CMS's though...