[qmailtoaster] how to control local infected users?

[Natalio Gatti]

Hello,
Yesterday, a local user was infected by a virus, and it start sending
thousands (100.000 aprox) of spam mails (it converted in a sort of
open-relay). Each mail only include 4 or 5 recipients.
My qmail-toaster accepted them, becouse the user was using smtp-auth, and
the user didn´t violate my chkusers policies.
How can I control such behaviour?

Natalio.