It is possible to detect an established SSH connection from your machine to a remote server. The lsof command can view an SSH connection. I am using SSH over port 443, so the connection is mixed up with a lot of other stuff that Firefox is connected to. But if…
Read MoreThe ss command for Linux allows a user to list all listening ports on a Linux system. This command lists all listening TCP ports. homer@deusexmachina ~ $ ss -l -t State Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN 0 1 127.0.0.1:4101 *:* LISTEN 0 50 *:netbios-ssn *:* LISTEN 0 128…
Read MoreHow to use ipgrab to capture TCP packets. The ipgrab command when run as root is very useful for capturing information about network packets that are traveling through your network interfaces. In this example I am capturing packets from my wlan0 interface. ubuntu ~ $ sudo ipgrab -i eth0 >…
Read MoreThis posting will explain the workings of the hping3 command. This is a command that may be run as the superuser to ping a website with TCP packets instead of the default ICMP packets used by the ping command. This is an example; I am sending some TCP SYN packets…
Read MoreAlternatives to the ping and traceroute commands on a Linux system There are many alternatives to the ping and traceroute commands on a Linux system. The mtr command is one of them. This command will trace the route the network packets are taking to the target IP address. bash 06:42:02…
Read MoreA nice script that will check if a host is up or not. #!/usr/bin/perl use warnings; use strict; use Net::Ping; # code source: http://www.perlmonks.org/?node_id=943892 # More: http://stackoverflow.com/questions/3960595/how-can-i-ping-a-host-with-a-perl-one-liner-with-netping #$| = 1; print "Please type a host to check: -:\n"; my $host = <>; #Reading input from STDIN….
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