We have recently changed our firewall settings to allow remote connections to our VoIP phone system. Although the home office workers are happy, this has allowed a flood of VoIP spammers to enter and try to connect to our server and phones.
I would like to fix this by utilizing a white-list at our firewall to only allow connections from our home users, who all use either Verizon FIOS or Time-Warner home connections.
I'm comfortable with this approach since 99.99% of the spam calls are from off-shore addresses. But they keep changing rapidly, so I don't want to try to manage an ever growing black-list.
Since they are home connections and are dynamically assigned, I can't just white-list one address and be done, it has to be the entire range that either of these two ISPs might assign to the home user.
Can anyone suggest a good way to find the entire range of public IP addresses that Verizon FIOS and Time-Warner utilize? I'd like to white-list as large a block of Verizon and TW addresses as possible to avoid a failure down the road.