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312 Chapter 13
domain controllers, or Active Directories, with or without SYSKEY installed. The
software is capable of sniffing encrypted passwords from the challenge/response
exchanged when one machine authenticates to another over the network. This software
allows administrators to match the rigor of their password audit to their particular needs
by choosing from three different types of cracking methods: dictionary, hybrid, and
brute force analysis. These methods are discussed in the next section. Finally, using
a distributed processing approach, LC4 provides administrators with the capability
to perform time-consuming audits by breaking them into parts that can be run
simultaneously on multiple machines.
13.2.4.2 Password Cracking for Self-Defense
Using a tool such as LC4 internally enables an organization’s password auditor to get a
quantitative comparison of password strength. This is done by reviewing LC4’s report
on the time required to crack each password. A Hide feature even allows administrators
the option to know whether a password was cracked without knowing what the password
was. Password results can be exported to a tab-delimited file for sorting, formatting or
further manipulation in applications such as Microsoft Excel. LC4 makes password
auditing accessible to less-experienced password auditors by using an optional Wizard
that walks new users through the process of configuring and running their password audit,
letting them choose from preconfigured configurations. As mentioned previously, when
performing the cracking process, three cracking methods (dictionary, hybrid, and brute
force analysis) are used. In his Web-based article [7] “ Hacking Techniques: Introduction
to Password Cracking, ” Rob Shimonski provides an excellent description of these three
methods, as follows:
1. Dictionary attack . A simple dictionary attack is by far the fastest way to break
into a machine. A dictionary file (a text file full of dictionary words) is loaded
into a cracking application (such as L0phtCrack), which is run against user
accounts located by the application. Because most passwords are simplistic,
running a dictionary attack is often sufficient to do the job.
2. Hybrid attack . Another well-known form of attack is the hybrid attack. A hybrid
attack will add numbers or symbols to the filename to successfully crack a
password. Many people change their passwords by simply adding a number to
the end of their current password. The pattern usually takes this form: first month
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