Hello,
during the testing period of Kamailio 3.1.0, while running it at voipuser.org, I had the chance to watch live and analyze a SIP scanning attack. Yesterday I noticed another one by looking at Siremis 2.0 charts, therefore I wrote an article with some hints about what you can use to protect your SIP services within Kamailio configuration file.
You can read it at: * http://asipto.com/u/i
Hope is going to be useful for many of you!
Cheers, Daniel