i noticed that in the usernmae it is always numbers on the end and you wont reconize the user. I know some posters have numbers on the end of their tag, but we know who they are and they are real. Usally the name of the spamers have a first last and numbers.. Also look for all CAPS of course. Yahoo tried to reduce the spammers but they were unsuccessful. They need to allow you to ignore users based on IP address as i am sure most of these users are using the same range of IP.
or they should allow you to filter messages as well.