Live view of Linux shell commands executed by another user?

Is it possible for the root user in Linux to have a real-time (or close to real-time) view of the shell commands being run by another user logged in via a terminal or SSH? Obviously they're stored in .bash_history, but that's only saved when the user logs off and can be disabled, too.

Edit: ideally something that can easily be switched on and off.

Solution 1:

as root, you could replace their shell with a simple wrapper script that logged their commands before passing them to the real shell. This would only work prior to them logging in.

Solution 2:

Use sniffy if you want to break into the user's session or screen -x if you have cooperation.

Be aware though, that spying on your users might be subject to regulations or even outright illegal depending on your local legislation.

Solution 3:

Changing the shell is very trivial to circumvent, patching the shell itself is better, but you have to patch all shells. Our favourite cracker uses this, as a bonus he doesn't bother himself with disabling bash_history.

ssh host /bin/sh -i  

Snoopy is a wrapper around exec functions, and logs any external binary that is executed(not shell builtins)

@David Schmitt's suggestion sniffy uses a better method, it taps the pseudoterminal.

ttysnoop uses the same method, but it is unmaintained. (I probably had issues making it log ssh connections, can't rememeber)

You can try patching ssh to log a session, but that patch is old.

pseudopod and rootsh can be used for logging legitimate sudos. And shwatcr is another thing to monitor logins.

Solution 4:

If you're being cooperative, you can use GNU screen between two users - have one establish the screen session, then have the other join using screen -x.

If you want root to "spy" on other users without their knowledge, the best and most efficient solution might be keylogger software/hardware.