Leetspeak passwords – predictable and crackable

Leetspeak — sprinkling your password with “4”s for “A,” “0”s for “O,” “$”s for “S” — has become a go‑to trick for users trying to satisfy complexity rules while keeping something vaguely memorable (e.g. P4$$w0rd). But the hard truth is these seemingly “clever” substitutions don’t fool attackers at all. In fact, they make your password incredibly fragile.

What is leetspeak?

Leetspeak (also known as 1337 speak) is a stylized form of writing that substitutes letters with numbers, symbols, or similar-looking characters — like replacing “E” with “3”, “A” with “4”, or “S” with “$”. Originally used in the 1980s by hacker subcultures to obscure messages in online forums and avoid detection, leetspeak has since become embedded in internet culture.

Today, leetspeak is often used (whether intentionally or subconsciously) when creating passwords. That’s largely due to password complexity requirements, which push users to include symbols and numbers. Rather than choosing truly random characters, users often take a familiar word and apply simple substitutions to meet those rules. For example:

• password → p@ssw0rd
• admin → @dm1n
• welcome → w3lc0m3

While these substitutions may satisfy complexity checks on paper, they offer little real security. Leetspeak transformations are well-known and easily accounted for in modern password-cracking techniques, making such passwords both predictable and vulnerable.

How leetspeak enables password cracking

Modern attackers don’t guess passwords randomly. Instead, they use highly efficient tools that exploit predictable user behavior. Whether it’s a basic dictionary attack or a high-speed brute-force operation, leetspeak often plays right into their hands.

Rule-based and dictionary attacks

The most common password cracking techniques involve applying rule-based logic to massive lists of known passwords and dictionary words. These tools simulate human behavior, running permutations like:

• Capitalizing the first letter
• Replacing “a” with “@”, “s” with “$”, “o” with “0”, etc.
• Appending digits like “1” or “123” at the end

This is where leetspeak becomes a liability. A password like “P4$$w0rd!” isn’t clever — it’s expected. Attackers apply these substitutions automatically, often within seconds.

Brute-force and hash cracking

In brute-force attacks, attackers attempt every possible combination of characters until the correct one is found. These are often used to crack hashed passwords where the original password has been encrypted using a one-way function.

Even with proper hashing and salting in place, weak or short passwords are still vulnerable. That’s because modern GPUs and cracking rigs can attempt billions of guesses per second. When users rely on leetspeak to add “complexity,” they’re typically reducing randomness and shrinking the overall keyspace.

The role of entropy

The real strength of a password comes from its entropy, AKA the measure of unpredictability. Each additional character in a password dramatically increases the time required to guess it through brute force.

Specops research analyzed 10 million real-world breached passwords and found that only 1.5% met the minimum threshold for true strength: 15 or more characters and at least two character types. At that length, even moderately complex passwords become practically uncrackable, taking millions or even billions of years to guess using current hardware.

In short, relying on leetspeak for “complexity” rather than length doesn’t strengthen your password. It just helps attackers crack it faster.

Tips for strong password security (because leetspeak won’t cut it)

Secure password practices go far beyond adding a few easily-cracked symbols. Here’s how to strengthen password hygiene in a meaningful, practical way:

1. Prioritize length over complexity

The single most effective way to improve password strength is to increase its length. A longer password expands the number of possible combinations exponentially, making it far more resistant to brute-force and dictionary attacks. Aim for at least 15 characters.

Length reduces reliance on arbitrary complexity (such as mixing symbols and numbers for the sake of passing a meter), and when implemented correctly, it’s easier to remember. For example, a password like MountainNight6OrangeSky is stronger, and far more memorable, than something like M0unt@1n!.

2. Use unique passphrases instead of substitutions

Rather than inserting leetspeak characters into common words (like turning “password” into “p@ssw0rd”), use unrelated, uncommon words to create a passphrase. A passphrase is a sequence of random or semi-random words that are easy to recall, but hard to guess. The UK National Cyber Security Centre recommends combining three random words to create a strong passphrase.

For example, a strong passphrase might look like: BlueChairTornado

It’s long, avoids dictionary phrases or popular quotes, and doesn’t rely on predictable substitutions. You can increase complexity further by adding a few symbols or punctuation marks, but only once the core structure is already secure due to its length and unpredictability.

3. Avoid common phrases and predictable patterns

Attackers use large datasets of breached passwords and common phrases when cracking passwords. These include pop culture quotes, song lyrics, and keyboard walk patterns (like “qwerty123“). Even minor changes, like adding a “!” or replacing letters with symbols like in leetspeak, won’t protect you if the base phrase is widely used.

When crafting a password or passphrase, always avoid:

• Popular sayings or slogans
• Consecutive number or letter sequences
• Common keyboard patterns (e.g. 1qaz2wsx)
• Common names, sports teams, birthdays, etc.

Instead, opt for random words that are memorable but have no public connection, and combine them in ways that don’t form logical sentences or predictable associations.

4. Enforce a strong password policy

Even the best password advice falls short if users are allowed to choose weak or compromised credentials. That’s why enforcing a strong password policy should be a non-negotiable for meaningful security.

A robust policy should go beyond outdated complexity rules (like requiring a symbol or uppercase letter) and instead focus on real-world password strength and threat mitigation. Here’s what that looks like in practice:

• Minimum length of 15 characters (or more)
• Blocking of commonly used and predictable passwords, including leetspeak variants
• Real-time checking against known breached passwords
• Protection against keyboard walk patterns and dictionary-based attacks

To enforce these standards effectively, organizations can implement a purpose-built solution like Specops Password Policy with Breached Password Protection. This solution integrates directly with Active Directory to block users from choosing passwords found in billions of known breaches, as well as blocking common weak passwords like usernames, display names and consecutive characters. Sign up for a free trial today.

5. Never reuse passwords

One of the most common and damaging mistakes users make is reusing passwords across multiple accounts. If one of those accounts is compromised, attackers will use credential stuffing to try the same combination elsewhere. This is especially dangerous when reused passwords are tied to email accounts, work credentials, or cloud storage.

Every account should have a unique password, especially for anything involving sensitive data, payments, or access to systems.

6. Enable multifactor authentication (MFA)

While not a password tip directly, MFA is a critical layer of protection in case a password is compromised. When enabled, it requires users to verify their identity through a second method, like an authentication app or hardware token, before granting access.

Where possible, enforce MFA on all accounts. This is particularly important for administrative access, email accounts, and services containing sensitive or business-critical information.

Ban weak passwords with Specops Password Policy

Protecting your organization starts with ensuring users can’t choose weak, predictable, or compromised passwords. That means enforcing more than just complexity rules. A strong password policy includes actively checking for:

• Known compromised passwords from breach data
• Common character substitutions
• Predictable keyboard patterns and reused variations

Specops Password Policy with Breached Password Protection closes the gaps that traditional complexity rules miss. It prevents users from falling back on unsafe habits and vulnerable patterns, ensuring every password is unique, unpredictable, and compliant with modern security standards. Specops Password Policy can block leetspeak, keyboard patterns, and even appending old passwords with a number or symbol.

Make password strength non-negotiable. Sign up for a free trial today to see how Specops Password Policy can improve your organization’s security.