Some people stated that such programs should not be made avail- able because they might help intruders to break into systems. The usual approach is to move the encrypted passwords to a so- called shadow password file that is accessible only to privileged programs. With shadow passwords an attacker can no longer run a password cracker on a stolen copy of the regular password file. Instead, one must connect to the machine to try a password. This makes the risk of detection much larger.
Shadow passwords can give a false sense of security, though.
It seems as if there is less need to be careful when choosing a password. After all, the encrypted password is protected from password cracking programs. However, it is easy to see how sha- dow passwords can actually weaken a system's defenses. In the second step, the login program is still privileged, so it can read the secret shadow password file. Not to mention the things that break as a side effect of fixing a non-problem.