6 Digit Otp Wordlist Fix (2024)

A "6-digit OTP wordlist" is a fundamental tool used in penetration testing to evaluate the security of One-Time Password (OTP) implementations. While mathematically simple, its effectiveness depends entirely on the target's defensive configurations. The Math: Keyspace & Probability

A standard 6-digit wordlist contains every numeric combination from 000000 to 999999, totaling 1,000,000 unique possibilities. Single Guess Success Rate: (0.0001%).

Brute-Force Speed: At a rate of 1,000 guesses per second, an attacker has a 50% chance of guessing the correct code in roughly 18.5 minutes if no other protections exist. Critical Evaluation

Predictability & Patterns: While wordlists typically run sequentially, research shows that humans choosing 6-digit PINs (often used as static OTPs or backups) frequently pick predictable patterns like 123456, 111111, or dates (DDMMYY). Security researchers often use "top 10" or "top 100" subsets of these wordlists to crack accounts faster, as 20% of all PINs can often be cracked with just a few attempts.

Bypass via Automation: Tools like Burp Suite Intruder allow testers to load these wordlists and automate thousands of attempts against a login endpoint. This is the primary "review" use case: checking if a server fails to block repeated failed attempts. Security Vulnerabilities Identified

A 6-digit OTP wordlist is only effective against systems with the following flaws: One-time passwords (OTP) - Security - MDN Web Docs

The List of Last Chances

The email arrived at 11:47 PM with the subject line: URGENT: master_wordlist_6digit_OTP_final.xlsx.

Maya deleted it twice. But it kept reappearing in her spam folder, each time with a new timestamp. On the third try, she opened it.

The file was small. Just one column (Column A) and 1,000,000 rows. No headers. Just every possible six-digit code from 000000 to 999999.

“A brute-force attacker’s bible,” she whispered. As a junior cryptographer, she knew this list by heart—it was the combinatorial key space of every SMS-based two-factor system on the planet.

But there was a second sheet. Titled used_codes.

It contained only 12 rows.

| A | |---| | 491202 | | 830415 | | 270591 | | 112233 | | 770101 | | 050503 | | 910910 | | 000007 | | 421988 | | 650211 | | 340923 | | 181206 |

Below them, in red text: “These were the last codes they entered before disappearing. Pattern them.”

Maya felt the cold crawl up her spine. She started with 491202. 49-12-02. December 2nd, 1949. Too old for a birthday. She tried 830415. April 15th, 1983. A birth year? Possibly. 270591 – May 27th, 1991. These were all dates.

She cross-referenced the first six entries against missing persons reports from a dark web archive she wasn’t supposed to access. Each date corresponded to the birthday of someone who had vanished within 48 hours of using that OTP to log into their bank, their email, their private server.

112233 was the outlier. No date. Just a lazy sequence. Its user was a 19-year-old who typed it into a “secure voting app” three hours before the election results were hacked.

770101 was January 1st, 1977—the birthday of a journalist whose last known action was approving a two-factor login from an IP address later traced to a decommissioned military satellite.

Maya’s hands shook as she typed 181206 into a search bar. It resolved to December 6th, 2018. The day her own mother had texted her: “Getting a weird code request. Ignoring it.”

Her mother never texted again.

The file wasn’t a wordlist. It was a graveyard keyed by six digits. Someone—or something—was using the universal OTP space not as a security measure, but as a summoning protocol. Every correct code opened a door. And on the other side, a listener collected the person who typed it.

Maya looked at the last row of the used_codes sheet. It was blank but for a blinking cursor.

Then her phone buzzed. New SMS: “Your verification code is: 041223.”

Below the message: “Enter to continue.”

She had 59 seconds before the code expired. And 59 seconds to decide if she wanted to join the list.

6-digit OTP wordlist is a comprehensive set of all 1,000,000 possible numerical combinations (from 000000 to 999999) used for testing the security of one-time password implementations. Core Features Complete Coverage

: Includes every possible combination to ensure no gap in brute-force or rate-limiting tests. Optimized Sorting

: Often ordered by probability (e.g., placing "123456" or "111111" first) to test for common vulnerabilities and weak generation algorithms. Predictive Entropy Testing

: Helps developers identify if their OTP generator is producing truly random codes or following detectable patterns. Security Auditing

: Used in penetration testing to verify that systems correctly implement account lockouts or "cool-down" periods after a specific number of failed attempts. Top 10 Most Common 6-Digit Codes Studies on PIN datasets like those from ResearchGate

show these are the most frequently guessed or used patterns: Technical Breakdown Total Combinations 10 to the sixth power (one million). Standard Length : 6 digits is the industry standard for platforms like Deutsche Bank

because it balances user effort with a "one-in-a-million" chance of a random guess. : Usually a simple

file for compatibility with security tools like Burp Suite or Hydra. to generate this wordlist or help prioritizing the list for a security audit?

Table 6 : Top ten 6-digit PINs in each PIN dataset - ResearchGate

Understanding 6-Digit OTP Wordlists: Security, Testing, and Risks

In the world of cybersecurity, a 6-digit OTP (One-Time Password) wordlist is a fundamental concept often discussed in the context of penetration testing, brute-force attacks, and multi-factor authentication (MFA) security.

If you are a security professional or a developer, understanding how these lists work—and why they are surprisingly simple to defend against—is crucial for building robust systems. What is a 6-Digit OTP Wordlist?

A 6-digit OTP wordlist is essentially a sequential or randomized list of every possible numerical combination from 000000 to 999999. 6 digit otp wordlist

Since an OTP is restricted to digits (0-9) and a length of 6, the math is straightforward: Total Combinations: 10610 to the sixth power (10 to the power of 6) Total Entries: 1,000,000 possibilities

Unlike complex password wordlists (like RockYou.txt) which contain billions of alphanumeric strings, an OTP wordlist is finite and relatively small. In a plain text format, a complete list of 1 million 6-digit codes takes up only about 7–8 MB of storage. Why People Use These Wordlists 1. Penetration Testing (The Ethical Use)

Security researchers use these lists to test the "rate-limiting" capabilities of a login system. If a website allows a user to try 100 different OTPs without locking the account or requiring a new code, it is vulnerable to a brute-force attack. 2. Understanding Entropy

Developers use these lists to study the randomness of their OTP generators. If a generator tends to produce numbers in the "middle" of the list more often than the "edges," the system's entropy is low, making it easier to predict. 3. Malicious Attacks

Hackers use automated scripts to cycle through these wordlists. Because there are only 1 million possibilities, a fast connection could theoretically test every single code in a matter of hours—if the target system doesn't have proper defenses. Why a Wordlist Isn't Enough: Modern Defenses

While 1,000,000 combinations might seem easy to crack, modern security standards make it nearly impossible to succeed using a simple wordlist.

Rate Limiting: Most reputable services will "throttle" or block an IP address after 3 to 5 failed attempts.

Short Expiry: OTPs usually expire within 30 seconds to 10 minutes. It is physically impossible to manual-input or even script-input 1 million combinations before the code changes.

Account Lockout: Beyond just blocking the IP, many systems will temporarily freeze the entire user account after repeated failed OTP entries.

Device Fingerprinting: Modern MFA systems look at the browser, location, and device. Even if you have the right code from a wordlist, an unrecognized device might trigger additional security hurdles. How to Generate a 6-Digit Wordlist for Testing

For those performing authorized security audits, you don't need to "download" a wordlist; you can generate one in seconds using a simple Python script:

# Generate a complete 6-digit OTP wordlist with open("otp_list.txt", "w") as f: for i in range(1000000): f.write(f"i:06d\n") Use code with caution.

This script creates a file where every number is padded with zeros (e.g., 000001, 000002), ensuring all 1,000,000 combinations are represented. The Verdict

A 6-digit OTP wordlist is a tool, not a "skeleton key." In the early days of the internet, a lack of rate-limiting made these lists dangerous. Today, they serve primarily as a reminder to developers: never deploy an authentication system without strict rate-limiting and short expiration windows.

If your system can be defeated by a simple list of 1 million numbers, the problem isn't the list—it's the architecture.

A 6-digit OTP (One-Time Password) wordlist consists of all possible numeric combinations from . This equates to exactly 1,000,000 unique entries

While simple in concept, these wordlists are essential tools for cybersecurity testing, development, and security analysis. 🔍 Wordlist Analysis

A standard 6-digit numeric wordlist has the following characteristics: Total Combinations : 1,000,000 (10^6) Storage Size : Approx. 7–8 MB when saved as a plain text file Security Strength

: Provides ~19.9 bits of entropy, making it significantly more secure than a 4-digit PIN (which only has 10,000 combinations) Predictability : Attackers often guess common patterns first, such as , or dates 🛠️ Common Uses Developers and security professionals use these lists for: The Mathematical Reason Your Passcode Should Repeat A Digit 4 Nov 2025 —

Subject: "6 Digit OTP Wordlist"

It was a typical Monday morning for cybersecurity expert, Alex, as she sipped her coffee and began to tackle the day's tasks. Alex worked for a company that specialized in penetration testing and cybersecurity assessments. Her current project involved testing the security of a new online banking system for a major financial institution.

As she booted up her computer, she received an email from her colleague, Jack, with the subject line "6 Digit OTP Wordlist." Jack was also part of the penetration testing team and was working on a different project.

Alex opened the email, expecting it to be a simple query about the project or perhaps a request for help. However, what she found surprised her. The email contained a single attachment titled "6_digit_otp_wordlist.txt" and a brief message:

"Hey Alex,

I came across this 6-digit OTP wordlist while researching potential vulnerabilities in authentication systems. I think it could be useful for our current and future projects. I've included it here. Let me know if you have any thoughts or if you'd like to discuss further.

Best, Jack"

Curious, Alex opened the attachment. It contained a list of 10,000 six-digit numbers. At first glance, it seemed like a simple list of random numbers, but as she scanned through it, she realized that these weren't just any numbers. They were potential one-time passwords (OTPs) that could be used to gain unauthorized access to systems that relied on six-digit OTPs for authentication.

Alex's mind began to race with the implications. If this list fell into the wrong hands, it could be used to compromise the security of any system that used six-digit OTPs. She quickly realized that she needed to take action.

She immediately replied to Jack's email, suggesting that they discuss the matter over a call. When they spoke, Jack explained that he had found the list on a publicly accessible forum while researching potential vulnerabilities in authentication systems. He had thought that sharing it with Alex could be beneficial for their work but hadn't considered the potential risks.

Alex and Jack decided to report the finding to their company's incident response team. The team took swift action, securing the list and reporting the potential vulnerability to the relevant authorities. They also began working on a plan to notify any organizations that might be affected by the potential leak.

As the day went on, Alex couldn't help but think about the potential consequences if the list had fallen into the wrong hands. She was proud of how quickly her team had responded to mitigate the risk. The experience reinforced the importance of vigilance in the field of cybersecurity and the need for constant communication and collaboration within their team.

The incident also led to a broader discussion within their company about the use of six-digit OTPs and the potential for similar vulnerabilities in their own systems. It was a valuable lesson in the ever-evolving landscape of cybersecurity threats and the importance of staying one step ahead.

Understanding 6-Digit OTP Wordlists: Security, Research, and Risks

In the world of cybersecurity and digital authentication, the "6-digit OTP" (One-Time Password) is the standard gatekeeper. Whether you are logging into your bank, verifying a social media account, or confirming a wire transfer, those six numbers are usually all that stand between a user and their sensitive data.

This has led to significant interest in 6-digit OTP wordlists. But what exactly are they, how are they used in security testing, and why is "brute-forcing" them much harder than it sounds? What is a 6-Digit OTP Wordlist?

A 6-digit OTP wordlist is a sequential or randomized list of every possible numerical combination from 000000 to 999999.

Because a 6-digit code is strictly numerical, the math is simple: Total Combinations: 10610 to the sixth power Range: 000,000 to 999,999 Total count: 1,000,000 possible codes.

In a "wordlist" format, this is typically a .txt or .lst file where each line contains one of these million possibilities. Why Do People Search for Them? A "6-digit OTP wordlist" is a fundamental tool

There are two primary reasons someone looks for a pre-generated 6-digit wordlist:

Penetration Testing: Security professionals use these lists to test if a web application has proper rate-limiting. If a system allows an automated tool to try thousands of codes without locking the account, it is vulnerable.

CTF Challenges: In "Capture The Flag" hacking competitions, participants often encounter simulated environments where they must script a solution to bypass an OTP check.

Security Research: Understanding the entropy and predictability of generated codes. The Myth of Brute-Forcing OTPs

While a 1,000,000-line wordlist might seem like a skeleton key, modern security measures make brute-forcing an OTP nearly impossible in a real-world scenario. 1. Rate Limiting and Account Lockout

Most platforms allow only 3 to 5 failed attempts before the account is locked or the IP address is throttled. Attempting to run a million-entry wordlist against a live API would result in a ban within seconds. 2. Expiration Time

OTPs are "One-Time" and time-sensitive. Most codes expire within 30 to 300 seconds. Even with a high-speed script, network latency makes it difficult to cycle through a significant percentage of a wordlist before the valid code changes. 3. Two-Factor Complexity

Modern 2FA (Two-Factor Authentication) often uses TOTP (Time-based One-Time Password) algorithms like Google Authenticator. The code is generated based on a secret key and the current time, meaning the "correct" code is a moving target. How to Generate a 6-Digit Wordlist (for Testing)

You don’t actually need to download a wordlist; you can generate one in seconds using simple command-line tools or Python. This is safer than downloading files from untrusted sources, which often contain malware. Using Python:

with open("otp_list.txt", "w") as f: for i in range(1000000): f.write(f"i:06\n") Use code with caution. Using Crunch (Linux/Kali): crunch 6 6 0123456789 -o otp_wordlist.txt Use code with caution. How Developers Protect Against Wordlist Attacks

If you are a developer, ensuring your 6-digit OTP system is secure involves more than just picking random numbers.

Implement Throttling: Use "exponential backoff." The more failed attempts, the longer the user must wait to try again.

Use True Randomness: Ensure your OTP generator uses a cryptographically secure pseudo-random number generator (CSPRNG).

Session Binding: Ensure the OTP is tied to a specific session ID so it cannot be reused or intercepted and applied to a different account. Conclusion

A 6-digit OTP wordlist is a fundamental tool for security auditing, but its effectiveness is neutralized by basic modern security protocols. For researchers, it serves as a reminder that entropy matters. For users, it highlights the importance of using services that implement strict lockout policies.

Are you looking to test a specific environment for rate-limiting vulnerabilities, or are you setting up 2FA for an application you're building?

This report examines the role of 6-digit OTP (One-Time Password) wordlists in cybersecurity, focusing on their use in penetration testing and the risks they pose to authentication systems. Executive Summary

A 6-digit OTP wordlist is a sequential or randomized collection of all possible numerical combinations from 000000 to 999999. While these lists are essential tools for security professionals to test the "brute-force" resilience of login interfaces, they also represent a primary method used by attackers to bypass Multi-Factor Authentication (MFA) when rate-limiting or account lockout policies are absent. 1. Composition and Scale

A complete 6-digit wordlist is mathematically finite and relatively small compared to alphanumeric password lists: Total Permutations: 10610 to the sixth power (1,000,000) possibilities.

Storage Size: Typically around 7 MB to 8 MB for a plain .txt file, making it highly portable and easy to load into memory for high-speed testing. Common Variants: Lists may be sorted numerically ( ) or by frequency ( ), as users often choose "predictable" codes if allowed. 2. Applications in Security Testing

Security researchers and penetration testers use these wordlists to identify vulnerabilities in the following areas:

Rate-Limiting Verification: Determining if a system blocks an IP or account after failed attempts.

OTP Prediction: Checking if the server-side generator produces truly random codes or follows a discoverable pattern.

Concurrency Issues: Testing if multiple rapid requests can "race" the system before a lockout is triggered. 3. Attack Vectors and Risks

If a service does not implement robust protections, a 6-digit wordlist can be used for:

Brute-Force Attacks: Systematically trying every code until the correct one is found.

Credential Stuffing: Combining known usernames with OTP automated guessing.

Reverse Brute-Force: Testing a common OTP (like 123456) against a large list of usernames. 4. Mathematical Probability of Success

The probability of guessing a 6-digit OTP depends on the number of attempts allowed before the code expires or the account is locked: As shown above, while the probability per attempt is low (

), automated scripts using wordlists can execute hundreds of attempts per second, making rate-limiting the only effective defense. 5. Recommended Mitigations

To defend against wordlist-based attacks, organizations should:

Implement Strict Rate-Limiting: Limit attempts to 3–5 tries per session/IP.

Short Expiration Windows: Ensure OTPs expire within 2–5 minutes.

Account Lockout: Temporarily freeze accounts after repeated failed MFA attempts.

Alphanumeric Codes: Transition to 8+ character alphanumeric codes to increase the search space exponentially.

In the world of cybersecurity, a 6-digit OTP (One-Time Password) wordlist

is essentially a document containing every possible numerical combination from

. While it looks like a simple list of numbers, it represents the front line of the battle between account security and "brute-force" hacking. The Anatomy of the List A complete 6-digit wordlist contains exactly 1,000,000 unique combinations The Range: It starts at and ends at The Purpose: The List of Last Chances The email arrived

Security researchers use these lists to test the "rate-limiting" capabilities of a system. If a website allows a user (or a bot) to try thousands of these numbers without locking the account, the system is vulnerable. The "Brute Force" Race

Imagine a digital vault protected by a 6-digit code. A hacker doesn't need to "guess" your specific code if they have a script that runs through a wordlist. The Script: An automated tool feeds the wordlist into a login field. The Speed: High-speed scripts can test hundreds of codes per second.

To find the one "needle" in the million-number haystack before the code expires (usually 30–60 seconds). Why Modern Security Wins

You might wonder why hackers don't just brute-force every OTP. Modern security systems are designed to make a 6-digit wordlist useless through three main methods: Rate Limiting:

Most apps lock you out after 3 to 5 failed attempts. Even with a million-number list, a hacker only gets five shots. Short Lifespans:

OTPs usually expire in under a minute. It is physically impossible to manually enter or even digitally cycle through a million options before the code changes. Account Throttling:

Systems detect rapid-fire entries from a single IP address and block the connection entirely. The Ethical Side In the hands of a Penetration Tester

(an ethical hacker), this wordlist is a diagnostic tool. They use it to ensure that a company’s "forgot password" or "login" screen properly rejects multiple failed attempts. If the wordlist works, the developer knows they need to add a "cooldown" timer or a CAPTCHA to protect their users. The takeaway?

A 6-digit code is only "weak" if the system behind it allows unlimited guesses. multi-factor authentication

(MFA) apps like Google Authenticator differ from SMS-based OTPs?

A complete 6-digit OTP wordlist consists of 1,000,000 unique combinations ranging from 000000 to 999999. These lists are primarily used for security testing (fuzzing) to identify vulnerabilities in systems that do not implement proper rate-limiting or account lockout policies. Wordlist Resources

For a "long post" style list, you can find full datasets hosted on repository sites like GitHub, which are designed to handle large text files:

SecLists (GitHub): A widely-used collection for security professionals containing the full range of 6-digit combinations.

Bug-Bounty-Wordlists (GitHub): Another curated list specifically for bug hunting and penetration testing.

Gigasheet Sample Data: A downloadable CSV version containing all 1 million rows for spreadsheet analysis. Top 10 Most Common 6-Digit PINs

While a full wordlist is sequential, many users choose predictable patterns. Research indicates these are the most frequently guessed combinations: 123456 111111 123123 654321 121212 000000 666666 123321 222222 456456

SecLists/Fuzzing/6-digits-000000-999999.txt at master - GitHub

SecLists/Fuzzing/6-digits-000000-999999. txt at master · danielmiessler/SecLists · GitHub. Not So Lucky Draw - Division Zero (Div0)

Title: An Analysis of Entropy and Feasibility in 6-Digit OTP Wordlist Generation

Abstract Six-digit One-Time Passwords (OTP) are the industry standard for Two-Factor Authentication (2FA) in banking, social media, and enterprise systems. While convenient, the limited keyspace of 6-digit numerical passwords presents a theoretical vulnerability to brute-force attacks. This paper explores the generation of "wordlists"—ordered lists of potential OTP values—analyzing the mathematical probability of successful prediction, the limitations of time-window constraints, and the efficacy of optimization strategies based on human password selection patterns.

1. Introduction Two-Factor Authentication (2FA) utilizing Time-based One-Time Passwords (TOTP) relies on the HMAC-based One-Time Password (HOTP) algorithm, often generating 6-digit numerical strings. The resulting password ($d$) falls within the range $000000 \le d \le 999999$.

The objective of a "wordlist" in this context is distinct from traditional password cracking. Unlike alphanumeric passwords where dictionary attacks target common phrases (e.g., "password123"), a 6-digit OTP wordlist targets the entire finite keyspace or optimized subsets of it based on generation logic or human bias.

2. Mathematical Constraints 2.1 The Keyspace A 6-digit numerical password has a fixed length $L=6$ using digits $0-9$. The total keyspace ($K$) is calculated as: $$K = 10^6 = 1,000,000 \text possible combinations.$$

2.2 Entropy The information entropy ($E$) of a 6-digit OTP is: $$E = \log_2(10^6) \approx 19.93 \text bits.$$ While roughly 20 bits of entropy is sufficient to deter manual entry, it is computationally trivial for modern hardware. A standard CPU can iterate through 1,000,000 integers in milliseconds. Therefore, the security of OTP relies not on the complexity of the value, but on the temporal constraints of the validation window.

3. Wordlist Generation Strategies In the context of security auditing and brute-force simulation, a "wordlist" for a 6-digit OTP can be generated using three primary methodologies:

3.1 Exhaustive Sequential Generation The most rudimentary wordlist is a simple text file containing integers from $000000$ to $999999$.

3.2 Human-Bias Optimization If the OTP is generated by a human (e.g., a user-chosen PIN for a banking app) rather than a cryptographically secure pseudo-random number generator (CSPRNG), patterns emerge. A targeted wordlist may prioritize:

3.3 Time-Sync Prediction (Theoretical) TOTP algorithms (RFC 6238) derive the OTP from the current Unix time divided by a time step (usually 30 seconds). $$OTP = Truncate(HMAC(K, T))$$ An advanced wordlist generation strategy involves predicting the server's time drift. If an attacker knows the precise server time, they can generate a targeted wordlist containing only the valid OTPs for the current and adjacent time windows (e.g., T-1, T, T+1), reducing the candidate list from 1,000,000 to typically 3 values.

4. Security Analysis and Rate Limiting The generation of the wordlist is not the bottleneck; the delivery mechanism is.

4.1 Rate Limiting Because the keyspace is small, systems implement strict rate limiting. A typical implementation locks the account or introduces exponential delays after 5 to 10 failed attempts.

4.2 Real-Time Replay Attacks In scenarios where an attacker intercepts an OTP (Man-in-the-Middle attack via phishing), the wordlist concept becomes obsolete. The attacker requires only a single specific value. However, "Realtime Replay" tools utilize a dynamic wordlist that is populated instantly upon the user entering their code, forwarding it to the attacker's session.

5. Conclusion The concept of a "6-digit OTP wordlist" highlights the fragility of low-entropy secrets. While generating a 7 MB text file containing every possible OTP is trivial, the utility of such a list is defeated by standard security controls like rate limiting and time-window expiration. The security of the 6-digit OTP system depends entirely on the inability of an attacker to submit the entries in the wordlist rapidly enough to exhaust the keyspace.

Appendix: Sample Wordlist Structure (First 10 and Last 5 entries)

000000
000001
000002
000003
000004
000005
000006
000007
000008
000009
...
999995
999996
999997
999998
999999

What Exactly is a 6-Digit OTP Wordlist?

A wordlist, in cybersecurity parlance, is a text file containing a list of potential passwords or codes. A 6-digit OTP wordlist is simply a text file containing all possible combinations of a 6-digit numeric code, or a subset thereof.

A full wordlist containing all one million codes would be approximately 6–7 MB (megabytes) as plain text—small enough to fit on a floppy disk from the 1990s. This small size is the root of the vulnerability.

1. Penetration Testing

White-hat hackers use OTP wordlists to test rate limiting, lockout policies, and the effectiveness of multi-factor authentication (MFA) implementations. A successful brute-force in a controlled environment reveals weak security controls.

The Comprehensive Guide to 6-Digit OTP Wordlists: Risks, Realities, and Defenses

2. Forensic Analysis

Incident responders may compare logs of attempted logins against known wordlists to identify patterns of attack or credential stuffing.

How to Defend Your Systems Against 6-Digit OTP Wordlist Attacks

If you are a developer or security professional, here are the golden rules to render OTP wordlists useless:

  1. Strict Rate Limiting: Allow no more than 5 failed OTP attempts per user per hour. After 3 failures, introduce a CAPTCHA or exponential backoff.
  2. Short Validity Window: OTPs should expire after 60-90 seconds maximum. Longer windows give attackers time to run wordlists.
  3. Never Allow Common PINs: If your OTP system allows users to set their own TOTP seed (rare, but happens for hardware tokens), reject the 200 most common codes just like you reject weak passwords.
  4. Use HMAC-based OTPs (HOTP) with a moving factor: Standard TOTP (RFC 6238) is fine, but ensure your implementation doesn’t allow replay attacks.
  5. Lockout after N attempts: After 10 consecutive global failures across any account, require admin intervention.
  6. Monitor for wordlist patterns: Your SIEM should alert on multiple failed OTP attempts that follow sequential order (e.g., 123456, 123457, 123458) or common PIN sequences.

Malicious Use Cases

The Hidden Danger of "6 Digit OTP Wordlist": Why It Exists and Why You Should Never Use One