Information
The /etc/shadow file is used to store the information about user accounts that is critical to
the security of those accounts, such as the hashed password and other security
information.
Rationale:
If attackers can gain read access to the /etc/shadow file, they can easily run a password
cracking program against the hashed password to break it. Other security information that
is stored in the /etc/shadow file (such as expiration) could also be useful to subvert the
user accounts.
Solution
Run the one of the following chown commands as appropriate and the chmod to set
permissions on /etc/shadow :
# chown root:root /etc/shadow
# chown root:shadow /etc/shadow
# chmod o-rwx,g-wx /etc/shadow