The following is a demonstration of the tcpsnoop program. Here we run tcpsnoop and wait for new TCP connections to be established, # tcpsnoop UID PID LADDR LPORT DR RADDR RPORT SIZE CMD 100 20892 192.168.1.5 36398 -> 192.168.1.1 79 54 finger 100 20892 192.168.1.5 36398 <- 192.168.1.1 79 66 finger 100 20892 192.168.1.5 36398 -> 192.168.1.1 79 54 finger 100 20892 192.168.1.5 36398 -> 192.168.1.1 79 56 finger 100 20892 192.168.1.5 36398 <- 192.168.1.1 79 54 finger 100 20892 192.168.1.5 36398 <- 192.168.1.1 79 606 finger 100 20892 192.168.1.5 36398 -> 192.168.1.1 79 54 finger 100 20892 192.168.1.5 36398 <- 192.168.1.1 79 54 finger 100 20892 192.168.1.5 36398 -> 192.168.1.1 79 54 finger 100 20892 192.168.1.5 36398 -> 192.168.1.1 79 54 finger 100 20892 192.168.1.5 36398 <- 192.168.1.1 79 54 finger 0 242 192.168.1.5 23 <- 192.168.1.1 54224 54 inetd 0 242 192.168.1.5 23 -> 192.168.1.1 54224 54 inetd 0 242 192.168.1.5 23 <- 192.168.1.1 54224 54 inetd 0 242 192.168.1.5 23 <- 192.168.1.1 54224 78 inetd 0 242 192.168.1.5 23 -> 192.168.1.1 54224 54 inetd 0 20893 192.168.1.5 23 -> 192.168.1.1 54224 57 in.telnetd 0 20893 192.168.1.5 23 <- 192.168.1.1 54224 54 in.telnetd 0 20893 192.168.1.5 23 -> 192.168.1.1 54224 78 in.telnetd 0 20893 192.168.1.5 23 <- 192.168.1.1 54224 57 in.telnetd 0 20893 192.168.1.5 23 -> 192.168.1.1 54224 54 in.telnetd 0 20893 192.168.1.5 23 <- 192.168.1.1 54224 54 in.telnetd 0 20893 192.168.1.5 23 -> 192.168.1.1 54224 60 in.telnetd 0 20893 192.168.1.5 23 <- 192.168.1.1 54224 63 in.telnetd 0 20893 192.168.1.5 23 -> 192.168.1.1 54224 54 in.telnetd 0 20893 192.168.1.5 23 <- 192.168.1.1 54224 60 in.telnetd 0 20893 192.168.1.5 23 -> 192.168.1.1 54224 60 in.telnetd 0 20893 192.168.1.5 23 <- 192.168.1.1 54224 60 in.telnetd 0 20893 192.168.1.5 23 -> 192.168.1.1 54224 72 in.telnetd [...] As new connections are made, each of the TCP packets are traced along with the UID, PID and command name. tcpsnoop has many options, for example here we use "-v" to print times, # tcpsnoop -v STRTIME UID PID LADDR LPORT DR RADDR RPORT SIZE CMD 2005 Jul 11 21:21:19 0 242 192.168.1.5 79 <- 192.168.1.1 49001 54 inetd 2005 Jul 11 21:21:19 0 242 192.168.1.5 79 -> 192.168.1.1 49001 54 inetd 2005 Jul 11 21:21:19 0 242 192.168.1.5 79 <- 192.168.1.1 49001 54 inetd 2005 Jul 11 21:21:19 0 242 192.168.1.5 79 <- 192.168.1.1 49001 56 inetd 2005 Jul 11 21:21:19 0 242 192.168.1.5 79 -> 192.168.1.1 49001 54 inetd 2005 Jul 11 21:21:19 0 23181 192.168.1.5 79 -> 192.168.1.1 49001 444 in.fingerd 2005 Jul 11 21:21:19 0 23181 192.168.1.5 79 -> 192.168.1.1 49001 54 in.fingerd 2005 Jul 11 21:21:19 0 23181 192.168.1.5 79 <- 192.168.1.1 49001 54 in.fingerd 2005 Jul 11 21:21:19 0 23181 192.168.1.5 79 <- 192.168.1.1 49001 54 in.fingerd 2005 Jul 11 21:21:19 0 23181 192.168.1.5 79 <- 192.168.1.1 49001 54 in.fingerd 2005 Jul 11 21:21:19 0 23181 192.168.1.5 79 -> 192.168.1.1 49001 54 in.fingerd [...]