At the first sign of trouble

[Patrick [ASE]]

If you are online, check your profile, change your password as described elsewhere, ensure email hasn't been changed.

If you think a 'cracker' using your account is online with you, log out, then login, this should force the cracker to be logged out as well, and they won't know your password as you changed it above.

May be a good idea to change email to one of the 'free accounts' or another account on your present one if allowable.

While we are talking about emails, if you join a strangers board, you could also use a different email and password

If you suspect a member of staff is doing things to your board, demote ALL staff if you don't know which one.

Disable signups if you get spammers, ban by the three methods (email, name and IP). you can post an email link on your board for prospective members to join your board. use a different email than your admin one(throwaway one)

[Patrick [ASE]]

Remember that a cracker could have got into the 2nd Admins or Gmods accounts, and if you have allowed them the full powers, they could do a lot of damage.
so if it looks like it could be your 2nd admin messing the board up, it could be a cracker, thats why you need to demote staff, if there's a problem.

and also why you need to tell your staff to follow the guide.