bot sentry is my motor (pidgin)
The instant messenger I'm currently using as my primary is Pidgin. This is one of those all-in-one things that connects to just about any chat network on the planet (AIM, ICQ, Yahoo, MSN, etc.)
Two of the chat networks I connect to, ICQ and Yahoo, have a spam problem. As if e-mail spam wasn't bad enough, now it was coming thru on my messenger. For ICQ I can understand the spam because that system is absolutely rampant with bots and spammers. But for Yahoo it's surprising. If you happen to use the from-Yahoo client (which most people do) you've probably seen the "report spam" option in it. This confirms that yes, it's a problem.
Pidgin is the only instant messenger client I know of in existence that has a bulletproof anti-spam plugin. It's called Bot Sentry and wow does it work well. The process of how it works is stupidly easy. If a message comes in from someone not on your contact list, Bot Sentry will ask the user a question. If the user gets it right, the user is "whitelisted" and you receive the message. If not, the user is put on your local blacklist.
Here are the top 3 reasons I'm lovin' Bot Sentry:
1. Blocks ALL spam.
2. If the user can't speak English, I never get the message.
Previous to using Bot Sentry I would get messages from people (meaning not bots or spammers) who could barely speak English on ICQ. It happened a lot and it was annoying.
3. Pick and choose which accounts have Bot Sentry enabled.
Whoever did this plugin really had the user in mind. For each account you have enabled in Pidgin you can enable or disable Bot Sentry, so it's not a "one-for-all". Very, very cool.
. . .
Instant messaging for me improved a lot by having this simple - and very effective - plugin installed. It's awesome.