mjhjmtu

If I and another person where logged onto a server (a Debian server to be exact) and I wanted to prevent the other user or even other user from seeing that I am active and logged into the server, how would I do that? Is there a command that I can use? If further clarification is needed, let me know.

There's not much you can do apart replacing commands such as w, who, ps etc. with a doctored version (modified on the source and then recompiled) whose output hides the user, say, huntert.

That's the technique usually used by intruders who compromise a server.

Note that an experienced Unix user might still be able to spot your presence by telltale signs, but this technique should fool the casual user -- or a lazy superuser.

Don't give them shell access.

If they have code execution, there's very little you can do to pervent that. Replacing binaries like @dr01 suggests is pretty much useless, because they'll just upload a clean version and use that instead. You could patch the kernel syscalls, but that's a lot of work, and probably not enough on its own.

Replace their login shell in /etc/passwd with something that only gives them access to the bare minimum that they need to have access to.