[toaster] Problem with virus

[Júlio Olivares]

Some months ago somebody from Brazil developed a virus that uses my free 
e-mail service to send information. The accounts had been disabled but I 
still got *thousands* of connections per hour that are rejected by the 
CHKUSER patch.
I'm looking for a way to get ride of these connections. I'm trying to 
implement a solution that uses iptbales to drop connections from ips trying 
to send mail from these accounts. I don't know if there's a better way, this 
was the first thing that occured me.
Because I'm not into C programming I don't know how to do it, any sugestions 
please ?

Thanks in advance,