How can I use shadow passwords?

Shadowing passwords stores users' hashed passwords in a different file, usually /etc/shadow on Linux systems, or /etc/master.passwd on BSD systems, which can be read only by root. Virtually all modern Linux distributions use shadowed passwords. This makes stealing passwords more difficult, as root access is required to find the hashed password. This was considered sufficient protection because a user with root permissions can find this or any data by other means, as he or she can examine the entire system, and could even subvert the passwd program to capture plaintext passwords. Unfortunately, some network authentication schemes operate by transmitting the encrypted password over the network, often making the data vulnerable to interception. Additionally, alternate copies of system data, such as system backups written to tape or optical media, become an alternate means for illicitly obtaining hashed passwords. The current trend in password security is making use of cryptographically stronger password hashes.