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Level: Intermediate
Presenter: Eli the Computer Guy
Date Created: November 1, 2010
Length of Class: 45 Minutes

Computer Security /Integrity

Knowledge of TCP/IP and Domain Name Resolution
Purpose of Class

This class teaches students how use DNS to redirect computer or network users to alternate websites or servers for security or malicious purposes.
Topics Covered

How DNS Works
Editing the HOSTS file
Alternate Public DNS
Planning a DNS Hack
Reasons to Hack DNS
Class Notes

DNS resolves Domain Names to IP Addresses
Warning: Use at your own risk
HOSTS file is the local file that resolves Domain Names
Windows Location = C:WindowsSystem32driversetc
Example =
In Vista/ Windows 7 First Open Notepad using “Run as Administrator” and then open the HOSTS file. Otherwise you will not be able to save your edits.
Computers FIRST try to Resolve a Domain Name with the HOSTS file, they then Go To the LOCAL DNS Server, and then they Query the PUBLIC DNS Server. If any server has a record the computer does not ask any other sources. SO if the HOSTS file has a record the computer uses that record and stops.
Using Alternate DNS
You do not have to use the Public DNS IP Addresses that your ISP gave you. You can use Alternate Public DNS Servers.
The benefit of using a server like is that they will prevent Domain Names for malicious websites from resolving. This is a HUGE security tool.
You can create your own Public DNS Server for Good/ Bad Purposes.
The DNS Attack
HOSTS file can be compromised either through manual editing, or through scripting. If users are logged in as USERS vs. ADMINISTRATORS there is far less chance that a script will be able to modify the HOSTS file.
By Wardriving or Plugging Into an Unsecured Network Jack You May be able to Hack the DNS Server. Routers/ Modems with default passwords are easy to Hack.
A clever, well disguised DNS Hack is very difficult to detect once it has been successfully implemented, and it is moderately difficult to circumvent if it is done by a network administrator to secure a network.
Final Thoughts
Hacking DNS is the EASIEST way to either protect or attack a network or computer