Classic Unix Security Problems

Password file

To avoid the most obvious problem, the passwords were scrambled
Password used as a key to DES-encrypt "\0\0\0\0\0\0\0\0"
Result stored in password file
You see the result of the encryption, but not the key that was used to get there
Problem: DES keys are only 56 bits
So you can easily mount a brute-force attack and get the root password
Even worse, you could prepare a cracking dictionary offline
If you acquire a password file later, look up the passwords in your dictionary
Get all the passwords instantly