Getting network routing information with Open Source tools
The tools in this category can be used to get the network routing information of a target. We will describe several tools that are commonly used for this purpose. Knowledge of the network routing information will allow the penetration tester to understand the network of the target machine, such as which path is taken by the packets sent from the penetration tester machine to the target machine.
The routing information will also give a clue as to whether the particular target is protected by firewall.
Let us see the several tools that can help you get routing information.
The TcpTraceRoute tool can be used as a complement to the traceroute command. The traceroute command sends a UDP or ICMP echo request packet with a Time To Live (TTL) of one and increments the TTL until the packet reaches the target, while the tcptraceroute tool uses TCP SYN to send out the packet to the target. The advantage of using tcptraceroute is that, nowadays, it is common to find a firewall device filtered traceroute packet, so it will not be possible to trace the network path to the target completely. However, this firewall still allows a packet to reach a particular TCP port in the target machine. By using tcptraceroute, we will be able to find the network path to the target, even though there is a firewall in front of it.
The tcptraceroute tool will receive a SYN/ACK packet if the port is open and a RST packet if the port is closed.
To access tcptraceroute, you can use the console and type the following command:
This will display usage information on your screen.
Let’s go for some action.
We run the traceroute command to trace our network route to the example.com domain as follows:
# traceroute www.example.com
The redacted result for this command is as follows:
traceroute to www.example.com (192.168.10.100), 30 hops max, 40 byte packets
1 192.168.1.1 (192.168.1.1) 8.382 ms 12.681 ms 24.169 ms
2 1.static.192.168.xx.xx.isp (192.168.2.1) 47.276 ms 61.215 ms 61.057 ms
3 * * *
4 74.subnet192.168.xx.xx.isp (192.168.4.1) 68.794 ms 76.895 ms 94.154 ms
5 isp2 (192.168.5.1) 122.919 ms 124.968 ms 132.380 ms...
15 * * *
30 * * *
After route number 15, we are no longer able to get the route information. Usually, this is because the traceroute packets are blocked by a filtering device.
We will try again using tcptraceroute, and we know that the targethost has an open TCP port for the web server (80). We can use the following command:
# tcptraceroute www.example.com
The result for this command is as follows:
Selected device eth0, address 192.168.1.107, port 41884 for outgoing packets
Tracing the path to www.example.com (192.168.10.100) on TCP port 80 (www), 30 hops max
1 192.168.1.1 55.332 ms 6.087 ms 3.256 ms
2 1.static.192.168.xx.xx.isp (192.168.2.1) 66.497 ms 50.436 ms 85.326 ms
3 * * *
4 74.subnet192.168.xx.xx.isp (192.168.4.1) 56.252 ms 28.041 ms 34.607 ms
5 isp2 (192.168.5.1) 51.160 ms 54.382 ms 150.168 ms
6 192.168.6.1 106.216 ms 105.319 ms 130.462 ms
7 192.168.7.1 140.752 ms 254.555 ms 106.610 ms
14 192.168.14.1 453.829 ms 404.907 ms 420.745 ms
15 192.168.15.1 615.886 ms 474.649 ms 432.609 ms
16 192.168.16.1 [open] 521.673 ms 474.778 ms 820.607 ms
This time, our packet is able to reach the target host, and it gives us all the route information from our machine to the target host.
Another tool that can be used to do route analysis is TcTrace. It works by sending a TCP SYN packet to the target.
To access tctrace, you can use the console and type the following command:
# tctrace -i<device> -d<targethost>
In the preceding command, –i is the network interface to the target and –d is the target.
To run tctrace to a target, the following command is used:
# tctrace -i eth0 -d www.example.com
The following result is obtained:
16(1) [192.168.16.1] (reached; open)