While the original icq client offers spam filtering, there is no such function in Gaim - though this is one of the most popular icq clients on linux systems.
The blocklist only works for a certain number of UIN and I get spam from new UIN everyday. And if it’s not about people contacting me and saying “hello” or some badly translated stuff, then they will send authorization requests that contain like 30 lines of text - hello? Why does this work? And why is there no plugin for gaim that filters messages or requests through spamassassin?

At least I’m not the only one with this problem: Tobias Schlitt has started a discussion on this topic in April and even announced that he would perhaps build an antispam plugin for gaim.