found this on the internet
# Adobe Real Time Messaging Protocol(RTMP). By Jonathan A.P. Marpaung
# Pattern attributes: works very fast
# Protocol Groups: streaming_video streaming_audio
# The RTMP Specification is availabe at
# http://www.adobe.com/devnet/rtmp/pdf/rtmp_specification_1.0.pdf [^]
# First 12 bytes, starting at \x03 are the RTMP header. Next 25 bytes,
# starting at \x02, are part of the RTMP body which is an AMF Object.
# The first string "connect" is a command of the NetConnection class object.
# The next string "app" is a Command Object which is followed by values
# such as "video", .
add a new pattern in ip->firewall->layer7 protocols
add a rule in ip->rfirewall->filter to block based on incoming interface (jn your case the wan) and your newly created l7 protocol, or based on destination ip (in your case local ip class) and your newly created l7 protocol.