Black Hat Bash - Bash Scripting for Hackers and Pentesters (Early Access) (Dolev Farhi, Nick Aleks)

$ sudo arp-scan 172.16.10.10 -I br_public

We also need to tell arp-scan which network interface to send

packets on, as there are a few network interfaces in Kali. To achieve

this, we use the -I argument. The br_public interface

corresponds to the 172.16.10.0/24 network in the lab.

To scan entire networks, you can pass arp-scan a CIDR

range, such as /24. For example, the following command scans all IP

addresses between 172.16.10.1 and 172.16.10.254:

$ sudo arp-scan 172.16.10.0/24 -I br_public

Lastly, you can make use of the hosts file you created in

“Generating a List of Consecutive IP addresses” on page XX as

input to arp-scan:

$ sudo arp-scan -f 172-16-10-hosts.txt -I br_public

The output generated by arp-scan should look like the

following:

172.16.10.10 02:42:ac:10:0a:0a (Unknown: locally administered)

172.16.10.11 02:42:ac:10:0a:0b (Unknown: locally administered)

172.16.10.12 02:42:ac:10:0a:0c (Unknown: locally administered)

172.16.10.13 02:42:ac:10:0a:0d (Unknown: locally administered)

It consists of three fields: the IP address, the MAC address, and

vendor details, identified by the first three octets of the MAC

address. In this scan, the tool identified four hosts on the network

that responded to ARP packets.

Exercise 3: Receiving Notifications When New Hosts Are Detected

Imagine that you want to be notified whenever a new host

appears on the network. For example, maybe you want to know

when new laptops or IT assets have connected. This could be useful

if you’re testing a target in a different time zone, where device users

might not be online when you are.

We can use bash to send ourselves an email whenever our script

discovers new assets. Listing 4-9 runs a continuous scan to identify

new online hosts, adds these to the 172-16-10-hosts.txt file we

created in “Generating a List of Consecutive IP Addresses” on page

XX, and notifies us of the discovery. We’ll walk through this code,

then discuss ways in which you can improve it.

#!/bin/bash