There is a very good article discussing Domino Security available at:
Contained within the article is a link to the following site which will ‘guess’ your ‘hashed’ password.
I am in no way affiliated with either link, but just thought they contained good information.
Subject: Domino Security Article - Very Informative
Good reminder for administrators enable the “Use more secure Internet Passwords” feature in the Domino Directory. This is found in the Domino Directory profile (under the actions menu). I believe this is disabled by default?