I have maybe a simple question about the security in RedHat 7.2. After an install several user accounts are created. Do I need to be concerned with changing these from the default passwords, or are they really needed?

i don't really think it would matter, but if you feel like its a security issue, you can always go in and change the passwords.

Maybe your confusing system with "human" users.
No install creates *user* accounts, unless you yourself do so, it creates system accounts and groups for the various parts of the system to work, like mail, uucp, nobody etc, etc.
These accounts don't have a password to work because then it would require human intervention to have em log in which is like reverse automation :-]

trickykid: your reply makes a lot of since, and I had actually thought about that. In doing that, will I need to change any thing in the bootup or services that may use these accounts?

UnSpawn: Your reply does not really make since to me. If an account is created then it has to have a passwaord or be null. What access do those account have? An example would be the adm account, which is also in a group called adm, what is the account for and why would the install create an account called adm if the account does not have rights to anything?

The daemon accounts don't need/allow a login. Have a look at the Linux Sysadm Guide.