In this section, we will grab the HTTP banner of a website. Banner grabbing or OS fingerprinting is a method to determine the operating system that is running on a target web server. In the following program, we will sniff the packets of a website on our computer, as we did in Chapter 3, Sniffing and Penetration Testing.

The code for the banner grabber is shown as follows:

import socket
import struct
import binascii
s = socket.socket(socket.PF_PACKET, socket.SOCK_RAW, socket.ntohs(0x0800))
while True:

  pkt  = s.recvfrom(2048)
  banner = pkt[0][54:533]
  print banner
  print "--"*40

Since you must have read Chapter 3, Sniffing and Penetration Testing, you should be familiar with this code. The banner = pkt[0][54:533] statement is new here. Before pkt[0][54:], the packet contains TCP, IP, and Ethernet information. After doing some hit and trail, I found that the banner grabbing information resides between [54:533].You can do hit and trail by taking slice [54:540...