With exception of root, the following is true:
1. None of those accounts have passwords.
2. You can not log into them.

To confirm this you would look in the /etc/shadow file. The password field in your shadow file should show that they have no password (look at /etc/shadow, the second field, separated by :, should be *). Most of these accounts will also have no shell (their shell will be /bin/false and home directory will be /dev/null). This means that even if someone were to some how log in as them, they wouldn't have a shell.