Minor spam outbreak on forum

Thios forum has always been astonishingly efficient at spam screening. I wonder what has changed in the last couple of days? Yesterday, when I checked for new messages, I found a reply in my 'Broken LOC' thread that was obviously spam (the title was a bit of a giveaway). Today, I received notice of a quarantined email with the following subject line and sender:

Subject: [Silverfrost Forums] free funny ringtones From: 'Silverfrost Forums' roza.smith@mail.com

It's not a big deal but I thought you would like to know that your previously impeccable standards seem to have been compromised somehow.

You do not need an account to post in the forums and as you say the spam is very little -- it is like that, we delete very little. If it continues we may have to go 'account' only -- which would be sad.

Administrator Silverfrost Forums

I see there has been a recent admin announcement as follows:

'Unfortunately these forums are being targeted by spam posters. We have therefore had to take away the anonymous posting feature. Anyone who posts to a thread will now need to be registered and logged-in.'

I have been the subject of another facet of this recent regrettable trend in the last couple of weeks. Every few days I get an email of the form 'An answer has been posted to your message on the page ...'. At first I assumed that each one of these really did correspond to another item of spam in one of my threads. However, this mornings offering was dated 23 Sept, 2 days after the most recent contribution to the forum. So, curious, I clicked on the URL (having checked that it really did resolve to 'forumspace', and sure enough it did not take me to a valid thread, but to a Silverfrost forums page saying 'there are no messages to display'. The URL in question was:

http://forums.silverfrost.com/forums/forum.asp?forumid=3&msg=2298#xx2298xx

Is anyone else getting this? Any suggestions as to how it is being implemented, or anything that can be done about it?

Andy