Currently, kerberized services do not make use of Pluggable Authentication Modules (PAM) — kerberized servers bypass PAM completely. However, applications that use PAM can make use of Kerberos for authentication if the pam_krb5 module (provided in the pam_krb5 package) is installed. The pam_krb5 package contains sample configuration files that allow services like login and gdm to authenticate users as well as obtain initial credentials using their passwords. If access to network servers is always performed using kerberized services or services that use GSS-API, such as IMAP, the network can be considered reasonably safe.
Administrators should be careful to not allow users to authenticate to most network services using Kerberos passwords. Many protocols used by these services do not encrypt the password before sending it over the network, destroying the benefits of the Kerberos system. For example, users should not be allowed to authenticate using their Kerberos passwords over Telnet.