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Firewall

  • In recent times, port probes, spam mail and also SIP attacks / SIP fraud have increased massively and it mostly comes from China, Korea and Palestine. If you run Linux as perimeter firewall, blocking those 3 (and any other you like) is fairly easy. This script downloads the respective network lists from ipdeny.com and inserts rules at the start of the INPUT and FORWARD chains, so IPs from any of those networks can neither reach your firewall not any system behind it.

  • If you run an Asterisk server which has the SIP ports exposed to the internet you have probably already noticed a ton of probes, connects which try to initiate calls to numbers with various prefixes. Although this doesn't do much harm if you did your homework and configured your Asterisk properly, it's still annoying. Here is how I deal with those: