This is part 2 of the Database Security Fundamentals series. In part 1, I provided an overview. Here I will cover basic access and authorization issues.

First, the basics:

Reset Passwords: Absolutely the first basic step is to change all default passwords. If I need to break into a database, the very first thing I am going to try is to log into a known account with a default password. Simple, fast, and it rarely gets noticed. You would be surprised (okay, maybe not surprised, but definitely disturbed) at how often the default SA password is left in place.
Public & Demonstration Accounts: If you are surprised by default passwords, you would be downright shocked by how effectively a skilled attacker can leverage ‘Scott/Tiger’ and similar demonstration accounts to take control of a database. Relatively low levels of permissions can be parlayed into administrative functions, so lock out unused accounts or delete them entirely. Periodically verify that they have not reverted because of a re-install or account reset.
Inventory Accounts: Inventory the accounts stored within the database. You should have reset critical DBA accounts, and locked out unneeded ones previously, but re-inventory to ensure you do not miss any. There are always service accounts and, with some database platforms, specific login credentials for add-on modules. Standard accounts created during database installation are commonly subject to exploit, providing access to data and database functions. Keep a list so you can compare over time.
Password Strength: There is lively debate about how well strong passwords and password rotation improve security. Keystroke loggers and phishing attacks ignore these security measures. On the other hand, the fact that there are ways around these security precautions doesn’t mean they should be skipped, so my recommendation is to activate some password strength checks for all accounts. Having run penetration tests on databases, I can tell you from first-hand experience that weak passwords are pretty easy to guess; with a little time and an automated login program you can break most in a matter of hours. If I have a few live databases I can divide the password dictionary and run password checks in parallel, with a linear time savings. This is really easy to set up, and a basic implementation takes only a couple minutes. A couple more characters of (required) password length, and a requirement for numbers or special characters, both make guessing substantially more difficult.
Authentication Methods: Choose domain authentication or database authentication – whichever works for you. I recommend domain authentication, but the point is to pick one and stick with it. Do not mix the two or later on, confusion and shifting responsibilities will create security gaps – cleaning up those messes is never fun. Do not rely on the underlying operating system for authentication, as that would sacrifice separation of duties, and OS compromise would automatically provide control over the data & database as well.
Educate: Educate users on the basics of password selection and data security. Teach them how to pick a word or phase that is easy to remember, such as something they see visually each day, or perhaps something from childhood. Now show them simple substitutions of the letters with special characters and numbers. It makes the whole experience more interesting and less of a bureaucratic annoyance, and will reduce your support calls.
All these steps are easy to do. Everything I mentioned you should be able to tackle in an afternoon for one or two critical databases. Once you have accomplished them, the following are slightly more complicated, but offer greater security. Unfortunately this is where most DBAs stop, because they make administration more difficult.

Group and Role Review: List out user permissions, roles, and groups to see who has access to what. Ideally review each account to verify users have just enough authorization to do their jobs. This is a great idea, which I always hated. First, it required a few recursive queries to build the list, and second it requires a huge list for non-trivial numbers of users. And actually using the list to remove ‘extraneous’ permissions gets you complaining users, such as receptionists who run reports on behalf of department administrators. Unfortunately, this whole process is time consuming and often unpleasant, but do it anyway. How rigorously you pursue excess rights is up to you, but you should at least identify glaring issues when normal users have access to admin functions. For those of you with the opportunity to work with application developers, this is your opportunity to advise them to keep permission schemes simple.
Division of Administrative Duties: If you did not hate me for the previous suggestion, you probably will after this one: Divide up administrative tasks between different admins. Specifically, perform all platform maintenance under an account that cannot access the database and visa-versa. You need to separate the two and this is really not optional. For small shops it seems ridiculous to log out as one user and log back in as another, but negates the domino effect: when one account gets breached it does not mean every system must be considered compromised. If you are feeling really ambitious, or your firm employs multiple DBAs, relational database platforms provide advanced access control provisions to segregate database admin tasks such as archival and schema maintenance, improving security and fraud detection.