Dê uma olhada neste script do Dtrace: conntrack
# ./conntrack -h
USAGE: ./conntrack [-h] [-p port] [-c command] [-u user]
-p port # filter by port (incompatible with user and command)
-c command # filter by command (incompatible with port and user)
-u user # filter by user (incompatible with port and command)
eg,
./conntrack -p 22 # snoop connections to port 22