PFSense Rule and reading contents of SIP packet

[srthomas]

Hi,

Can anyone tell me if PFSense can look into a SIP packet and examine it to strings?

I'd like to implement this type of security as an addition:

http://www.sunshinenetworks.com.au/how-to/91-secure-your-voip-server-with-the-sunshinenetworks-knock.html

Thanks