There are multiple forms of credential attack, but all too often, they are considered as the last step in a penetration test, when all else has failed. This is because most new assessors approach it in the wrong manner. When discussing what brand new assessors use for credential attacks, the two most common attacks used are online dictionary and brute force attacks. They execute a credential attack by downloading a giant word list containing passwords and an extensive username list and run it against an interface. When the attack fails, the assessor follows up and executes a brute force attack.
This attack uses either the same username list or the super user (root) or the local administrator account. The majority of the time this will fail as well, so in the end dictionary attacks get a bad rap and get moved to the end of the engagement. This is ever so wrong, as on most engagements, especially on Internet facing postures a credential attack...