Nobody has specifically mentioned whether the spam messages are appearing in WC. I do know this happens. I happen to use the Chat Guard No Spam addon from Curse. Ive had guildies complain about WC spams, but the
only times I've ever seen them have been immediately after logging in. They show up
once in one of the little pop-up windows (which I normally have set to be disabled), but the spams themselves never show up in my chat log. So, I would hazard a guess that Chat Guard is generally working. It may be that it hasn't quite loaded completely and a single WC spam manages to make its way in on my display, but only
once. (Unfortunately, it seems to be the same spam website, though it's made by a different spam bot each time.)
It's been mentioned a number of times before that /say chat spammers can
not be blocked by addons such as Chat Guard. The best solution is to use the Report Tool at
http://report.runesofmagic.com/index.php which will flag that specific spam bot for a cleanup on Aisle 3.