From one of the mailing lists:
Recently we have been hit by the attackers during the weekend causing more
than 100 K USD bill
They were dialing payphone type numbers” dial to win” by compromsing one of
our DID number.
Mostly calls were placed to Lithuania, and sierraleone.
But guys buckle up, there are some gangs using sophisticated mechanisms to
get into IP PBX systems
Remove all NAT with local IPs, block SIP ports and h.323 ports, if u r using
cisco upgrade to v15.12T.
add trusted gateway list.
One way to document and block hackers, is to implement a VoIP Abuse list.
Have a look at VoIP Abuse Blacklist implentation.
Sjur Usken 