pidgin privacy please is a pidgin plugin to stop spammers from annoying you. You can block messages from certain users, block messages from people who are not on your contact list, and suppress repeated authorization requests. Optionally, senders of blocked messages can be notified with an auto-reply.
CAPTCHAv2 is a question/answer based CAPTCHA system. It has been designed to protect any Web form from spam bots attempting to submit information automatically by asking questions the visitor needs to answer. It can also detect brute force attempts and will block further abuse by adding the visitor's IP address to the .htaccess file. CAPTCHAv2 prevents accidentally blocking good bots by verifying the whois record of the visitor's IP. It is also possible to use CAPTCHAv2 as an automatically blocking bot trap. Bot trap implementation guide can be found in the guides.