[App_rpt-users] Messages log file question

Hi, Is there any way that I can stop the Indian hackers who are constantly trying to find a valid extension / password combination on my SIP gateway into the repeaters? They're using up a bunch of my capped internet bandiwdth and making 10 days worth of messages log over 24Mb! If not, is there a way to stop such attempts filing the messages log with megs and megs of this stuff? Thanks Matt G4RKY