Not a plugin, it's a program that plays the game for you. I doubt spammers use it, they'd probably use something more along the lines of an actual bot for that - but I mean, with very simple macros you can spam anywhere.
Easy macro ex:
/1 HEAD TO WOWXXX.COM TO BUY GOLD!
/2 HEAD TO WOWXXX.COM TO BUY GOLD!
/3 HEAD TO WOWXXX.COM TO BUY GOLD!
/4 HEAD TO WOWXXX.COM TO BUY GOLD!
And all you have do is click a little icon on your action bar and it sends the message(s). I'll edit this later and go into more detail, I've been up for almost two days straight now
The thing is, spammers aren't going to want to do all that manually, the idea is to automate it. Are there any actual bots? I thought Warden was doing a good job preventing them?
And what about getting the gold that spammers sell? And powerleveling? I imagine that could be done through WoWGlider, correct?
It wouldn't be to hard to write a program to manifest itself in the client and hook key calls (much like WoWGlider). This would automate Macro sending. All they really did was send messages to everyone on the server or in a zone simultaneously.
There is however, no doubt that they use Bots. How exactly they circumvent Warden if they take this route, I'm not sure. Things like mass spamming in game mail and being invited to a Party full of Bots to be spammed can't be automated (Easily).
As for the WoWGlider for Gold/PL. It's not that widely used due to the fact that Warden is always detecting it, and it's just basically a cat and mouse game. This banwave shows how unreliable such means can be, and would cause a gold/pl company to lose a lot of money.
What they have been found to do is pay people in other countries very low wages to kill mobs for gold and to power level characters for people.