Thanks Louise. I have cleaned it all up and removed the spammer.
I have also given veterans the power to remove spam by active members (previously they could only do so when the spam was by new members).
To answer some of the questions...
Spammers get in like anyone else. They register an account and then start posting. If they wait for more than a week before starting to post spam then after 5 quick posts they ascend to active member level.
It is sufficient to report one post by the spammer, but reporting more than one does give us a sense of the severity of the problem.
For veterans, removing more than one spam post by a spammer is important, because after a certain number of these the system suspends the spammer so I can take a look before they do any more damage.
Thanks for all the help. Spam is a scourge of the Internet and we're determined to keep it out of YLF.