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Crafting a Custom Dictionary for Your Password Policy

Updated: Nov 15, 2022

Modern password policies are comprised of many different elements that contribute to its effectiveness. One of the components of an effective current password policy makes use of what is known as a custom dictionary that filters out certain words that are not allowed as passwords in the environment.

Using custom dictionaries, organizations can significantly improve their cybersecurity posture and filter out obvious passwords that provide poor security for user accounts.

When using password dictionaries in your password policy, there are many different approaches to consider. First, let’s consider crafting a custom dictionary for your password policy, including general guidance on how these are created, configured, and how you can easily use custom dictionaries in an active directory environment.

Why customize your dictionary?

Custom dictionaries are born from the need to “think as a hacker thinks.” Compromised credentials are one of the leading causes of malicious data breaches across the board. They are also one of the most expensive to organizations. IBM’s Cost of a Data Breach Report 2020, compromised credentials increased the average total cost of a breach by nearly $1 million to $4.77 million.

Hackers often use credential-based attacks to compromise weak passwords, passwords that have been previously breached, common passwords used in a specific business sector, or common spelling transformations.

Unfortunately, all of us tend to use passwords that we can easily remember. In addition, end-users often add common numbers or symbol patterns to the beginning or end of passwords to get around password complexity requirements.

Both human nature and the technology tools available allow easily cracking or guessing weak, standard, or expected passwords. While attackers have access to large databases of breached and otherwise common or weak passwords, the “good guys” can implement a password file in a good way – the custom dictionary.

The custom password dictionary works in favor of securing the passwords in your environment.

When implemented, the custom dictionary provides a means to filter the chosen password or end-users in such a way as to disallow passwords or variations of the passwords contained in the custom dictionary.

So, aren’t all passwords that meet the Active Directory Password Policy requirements secure? Not exactly.

While password policy requirements defined by Active Directory Password Policy are a good starting point, they leave much to be desired when considering the cracking and other password tools that cybercriminals are using today.

As an example, a password policy may require that an end-user meet the following requirements:

  1. Minimum of 8 characters

  2. Password must meet complexity requirements (Must contain uppercase, lowercase, numbers, and non-alphabetic characters such as symbols)

Specops Password Policy

A password policy defined in Active Directory Domain Services

Using the native Active Directory Password Policy settings above, a user could potentially set passwords such as:

  1. P@$$w0rd123

  2. MybusinessName123!

  3. Letmein1$

The above passwords meet all the criteria defined as part of the length and complexity requirements.

However, they are weak and easily guess due to different reasons. As the above examples show, these could be known variants of common words such as “Password,” related to your specific business name or industry, or a common phrase contained in a cracked password database such as “Letmein1$.”

Downloadable custom password dictionaries

You may not want to “reinvent the wheel” when it comes to gathering passwords to use in a custom dictionary for your password policy. There are out-of-the-box password dictionaries and password files that can be freely downloaded as the basis for a custom password dictionary. An example includes the Have I Been Pwned password list: Have I Been Pwned: Pwned Passwords.

Companies can also use readily available tools such as Crunch, available in Kali Linux or installable from your Linux distribution repository. In Ubuntu, you can install Crunch using the command:

  1. sudo apt-get install crunch

It allows creating a wordlist that can be used for brute force or password strength auditing by SecOps teams in your organization. In addition, these readily available tools can provide the basis for creating your own custom password lists in your environment.

Employing a Password filter .dlls

However, there is more involved than simply creating a password dictionary file. Organizations that want to implement their own custom password filter .dll, along with words containing their business name or industry-specific keywords, must have the development talent and resources available to create the .dll file needed for the password filter functionality in Active Directory.

Microsoft outlines the process of registering and installing a password filter .dll here: Installing and Registering a Password Filter DLL – Win32 apps | Microsoft Docs.

Custom dictionary solutions in your password policy tools

Is there an easy way to craft a custom dictionary for your password policy? Specops Password Policy takes the harder work out of implementing custom dictionaries for your password policies and allows for the negation of over 2 billion known breached passwords plus any customized terms like your company name, or location, to be added to a password policy tool.

High-quality password policy tools like this integrate with your native Active Directory Password Policies implemented at the Group Policy level.

With simple checkboxes, the Specops solution allows IT admins to easily and quickly implement multiple password dictionaries as part of the password rules configured for their organization.

Specops Password Policy

Specops Password Policy dictionary settings

Specops Password Policy

Configuring the Use custom dictionaries allows importing password files, hash files, or creating new dictionaries right from the interface.

Under the downloaded dictionaries configuration, admins have access to readily available password dictionary files that can be downloaded directly from the Specops Password Policy interface.

Specops Password Policy

Downloading password dictionary files from the Specops Password Policy interface

Specops Password Policy makes configuring, implementing, and maintaining custom dictionary files for your organization’s password policy easier—with no programming knowledge or expertise required.

Get started using a custom dictionary in your password policy

Organizations today must bolster the security of account passwords to strengthen their overall cybersecurity posture. Using custom dictionaries as part of their password policies is a great way to factor in an offensive strategy to your cybersecurity efforts.

However, implementing a custom password filter .dll in the environment requires developing the custom password filter .dll file required by Active Directory. This development can present roadblocks to businesses implementing custom dictionaries like cost, maintenance, and efficiency blockers.

Specops Password Policy allows implementing multiple custom dictionary files with just a few clicks, eliminating the complexity and security issues involved with implementing this correctly.

Is your business fully prepared for an event that could destroy all of the data you possess? 

Talk to our Cyber and Network Security experts and ensure you’re taking ALL of the NECESSARY steps to ensure you are protected.

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