Every computer must have an administrator: someone who can install software, configure the operating system, add and manage user accounts, establish security policies, and handle all the other management tasks associated with keeping a computer up and running. By definition, these tasks require that he have control over the computer. This puts the administrator in a position of unequalled power. An untrustworthy administrator can negate every other security measure you've taken. He can change the permissions on the computer, modify the system security policies, install malicious software, add bogus users, or do any of a million other things. He can subvert virtually any protective measure in the operating system, because he controls it. Worst of all, he can cover his tracks. If you have an untrustworthy administrator, you have absolutely no security.
When hiring a system administrator, recognize the position of trust that administrators occupy, and only hire people who warrant that trust. Call his references, and ask them about his previous work record, especially with regard to any security incidents at previous employers . If appropriate for your organization, you may also consider taking a step that banks and other security-conscious companies do, and require that your administrators pass a complete background check at hiring time, and at periodic intervals afterward. Whatever criteria you select, apply them across the board. Don't give anyone administrative privileges on your network unless they've been vettedand this includes temporary employees and contractors, too.
Next, take steps to help keep honest people honest. Use sign-in /sign-out sheets to track who's been in the server room. (You do have a server room with a locked door, right? If not, re-read Law #3.) Implement a " two-person " rule when installing or upgrading software. Diversify management tasks as much as possible, as a way of minimizing how much power any one administrator has. Also, don't use the Administrator accountinstead, give each administrator a separate account with administrative privileges, so you can tell who's doing what. Finally, consider taking steps to make it more difficult for a rogue administrator to cover his tracks. For instance, store audit data on write-only media, or house System A's audit data on System B, and make sure that the two systems have different administrators. The more accountable your administrators are, the less likely you are to have problems.