10.3.9.1. Traditional

Traditionally, users are authenticated locally, using the information stored in /etc/passwd and /etc/shadow on each system. But even when using a network service for authenticating, the local files will always be present to configure system accounts for administrative use, such as the root account, the daemon accounts and often accounts for additional programs and purposes.

These files are often the first candidates for being examined by hackers, so make sure the permissions and ownerships are strictly set as should be:

bob:~> ls -l /etc/passwd /etc/shadow
-rw-r--r--    1 root     root         1803 Mar 10 13:08 /etc/passwd
-r--------    1 root     root         1116 Mar 10 13:08 /etc/shadow