CEH

160 Chapter 7 ■ Gaining Access to a System

With all the hashes generated ahead of time, it becomes a simple matter to compare the

captured hash to the ones generated, typically revealing the password in a few moments.

Of course, there’s no getting something for nothing, and rainbow tables are no excep-

tion. The downside of rainbow tables is that they take time. It takes a substantial period of

time, sometimes days, to compute all the hash combinations ahead of time. Another down-

side is that you can’t crack passwords of unlimited length, because generating passwords of

increasing length takes more time.

Generating Rainbow Tables

You can generate rainbow tables many ways. One of the utilities you can use to perform

this task is winrtgen, a GUI-based generator. Supported hashing formats in this utility

include all of the following:

■ Cisco PIX

■ FastLM

■ HalfLMChall

■ LM

■ LMCHALL

■ MD2

■ MD4

■ MD5

■ MSCACHE

■ MySQL323

■ MySQLSHAl

■ NTLM

■ NTLMCHALL

■ OR ACLE

■ RIPEMD-160

■ SHA1

■ SHA-2 (256), SHA-2 (384), SHA-2 (512)

EXERCISE 7.2

Creating Rainbow Tables

Let’s create a rainbow table to see what the process entails. Keep in mind that this process

can take a while once started.