Information
The /etc/shadowfile 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/shadowfile, they can easily run a password cracking program against the hashed password to break it. Other security information that is stored in the /etc/shadowfile (such as expiration) could also be useful to subvert the user accounts.
Solution
Run the one following commands to set permissions on /etc/shadow:
# chown root:shadow /etc/shadow
# chmod o-rwx,g-wx /etc/shadow