What is the "card cracking" technique and how does it use brute force to select card data?

[Student]

Card cracking is a form of cybercrime aimed at obtaining or verifying bank card data (card number, expiration date, CVV code, and, if applicable, cardholder name) for subsequent use in fraudulent transactions, such as unauthorized purchases, withdrawals, or the sale of valid data on the black market. Card cracking often utilizes brute-force attacks in combination with automated tools to achieve its goals. Let's explore the process in more detail, including technical aspects, examples, tools, and security methods, to provide a thorough understanding for educational purposes.

1. What is card cracking and its place in cybercrime?​

Card cracking is a process aimed at determining the validity of bank card data. It is part of a broader category of fraud known as carding, in which valid card data is used for financial gain. Card cracking focuses specifically on the verification or data selection stage to confirm that a card can be used.

Fraudsters who engage in card cracking often work with large data sets (dumps), which can include thousands or millions of card numbers obtained through:

• Data leaks from online store databases, payment systems, or banks.
• Phishing (e.g. fake websites that mimic payment pages).
• Skimmers (devices that read data from the magnetic strip of a card at ATMs or terminals).
• Purchase on the darknet black market, where lists of cards with partial data are sold.

The goal of card cracking is to turn this partial data into a complete set suitable for fraud.

2. Bank card data structure​

To understand how card cracking works, it's important to understand what card details are required to complete a transaction:

• Card number (16 digits for most cards, such as Visa, Mastercard; 15 for American Express):
  • The first 6-8 digits are the BIN (Bank Identification Number), which identifies the bank and card type (debit, credit, etc.).
  • The remaining numbers are a unique account identifier.
• Expiry date (month and year, e.g. 12/27).
• CVV/CVC code (3 digits for Visa/Mastercard, 4 for AmEx, usually on the back of the card).
• Owner's name (sometimes required, but not always).
• Billing address (may be required for some transactions, especially in countries with strict requirements).

Fraudsters often have only part of this data (for example, the card number), and the rest is obtained using brute force.

3. How is brute force used in card cracking?​

Brute-force is a method of trying all possible combinations to find unknown data. In the context of card cracking, it is used to determine missing elements, such as a CVV code or expiration date. Here's how it works step by step:

3.1 Data preparation​

• The scammer begins by typing card numbers, which can be obtained from dumps. For example, a dump might contain:
  

  4123456789012345
  5234567890123456
  6011123456789012

• These numbers may not have a CVV or expiration date, as this data is often not stored in databases (in accordance with PCI DSS requirements).

3.2. Combination generation​

• For each card, the program generates possible combinations of missing data:
  • Validity: Typically, all months (01-12) and the next 4-5 years (e.g. 2025-2030) are cycled. This gives approximately 60 combinations per card (12 months x 5 years).
  • CVV code: For Visa/Mastercard it is 000–999 (1000 combinations), for AmEx it is 0000–9999 (10,000 combinations).
• Example of combinations for card 4123456789012345:
  

  4123456789012345 | 12/25 | 123
  4123456789012345 | 12/25 | 124
  4123456789012345 | 01/26 | 123
  ...

3.3. Automated verification​

• Fraudsters use specialized programs such as OpenBullet, Sentry MBA, BlackBullet, or custom scripts that send these combinations to websites for verification.
• The check is carried out through:
  • Payment gateways: Attempts to charge small amounts (e.g. $0.01–$1) on sites with poor security.
  • Linking a card: Some services (for example, trial subscriptions) check the card, making a temporary authorization without debiting funds.
  • Donations: Donation sites often do not require 3D-Secure for small amounts.
• If the request is successful (for example, the site accepts the card), the data is saved as "valid." If not, the program moves on to the next combination.

3.4. Bypassing restrictions​

To avoid detection, scammers use:

• Proxy servers or VPNs: To mask your IP address and simulate requests from different regions.
• User-Agent Rotation: Changing browser data to make requests appear to come from different devices.
• Anti-bot protection: Bypassing CAPTCHA using automatic recognition services (e.g. 2Captcha) or manual input.
• Small amounts: Testing with minimal transactions reduces the likelihood of triggering bank monitoring systems.
• Distributed attacks: Using botnets to check multiple sites in parallel.

3.5. Example scenario​

Let's assume a fraudster has card number 4123456789012345 and wants to guess the CVV and expiration date:

• The program generates 60 × 1000 = 60,000 combinations (12 months × 5 years × 1000 CVV).
• It sends requests to a site that accepts donations without 3D-Secure, for example $1.
• If the server response indicates successful authorization (e.g. HTTP code 200 or "Payment successful" message), the card data is saved:
  

  4123456789012345 | 06/27 | 456

• The card can now be used for large purchases or sold on the black market.

4. Card Cracking Tools and Platforms​

Fraudsters use specialized tools that simplify the process:

• OpenBullet: A popular open-source tool for automated testing. It allows you to create configurations for testing on specific websites.
• Sentry MBA: An outdated but still used mass brute force tool.
• BlackBullet: A modern alternative with proxy and CAPTCHA support.
• Custom scripts: Written in Python, PHP or other languages for specific tasks.
• Combolists: Lists of cards (number + CVV + expiration date) that are loaded into checkers for bulk verification.

These tools are often distributed on darknet forums such as RaidForums (before it was shut down) or similar sites.

5. Vulnerabilities Exploited by Card Cracking​

Card cracking is possible due to vulnerabilities in the online payment ecosystem:

• Lack of 3D-Secure: Some websites, especially in certain regions, do not require additional authentication (password or code from SMS).
• Weak brute force protection: No limit on the number of attempts to enter card data.
• Outdated payment gateways: Some platforms do not check suspicious patterns (for example, hundreds of requests from one IP).
• Small transactions: Banks may not block small transactions, considering them safe.
• Data Leaks: Card dumps available on the dark web provide scammers with raw data.

6. Consequences of card cracking​

• For users:
  • Financial losses if fraudsters manage to complete transactions.
  • Inconveniences associated with card blocking and the need to reissue it.
  • Possible compromise of personal data.
• For merchants:
  • Losses due to chargebacks (refunds) if the cardholder disputes the transaction.
  • Reputational risks.
  • Additional costs for implementing protection.
• For banks:
  • Increase in the number of fraudulent transactions.
  • The need to strengthen monitoring and protection systems.

7. Methods of protection against card cracking​

For users:​

• Use 3D-Secure: Activate two-factor authentication for all cards (Verified by Visa, Mastercard SecureCode, Mir Accept).
• Transaction Monitoring: Activate SMS or push notifications from your bank to track all transactions.
• Transaction limits: Set limits on online payments or temporarily disable them when the card is not in use.
• Virtual Cards: Use disposable or virtual cards for online purchases.
• Avoid suspicious sites: Do not enter card details on unverified platforms.
• Change passwords regularly: Use complex passwords and two-factor authentication for banking apps.

For merchants:​

• 3D-Secure implementation: Mandatory authentication for all transactions.
• Attempt Limit: IP blocking after several unsuccessful attempts to enter card data.
• CAPTCHA: Use CAPTCHA to prevent automated queries.
• Monitoring systems: Analysis of transaction patterns to identify suspicious activity (e.g. multiple requests from one IP).
• Updating payment gateways: Using modern standards such as PCI DSS.

For banks:​

• Anti-fraud systems: Using AI to analyze transactions in real time.
• Blocking suspicious transactions: Automatic blocking upon detection of brute force attacks.
• Customer education: Information on the safe use of cards.

8. Attack example (hypothetical scenario)​

1. A scammer buys a dump of 10,000 card numbers on the darknet for $50–$100.
2. He uploads the list to OpenBullet and configures it to check against a donation site that does not require 3D-Secure.
3. The program uses proxies (e.g. 100 different IP addresses) and generates CVV and expiration date combinations.
4. In an hour, the program checks 5,000 combinations and finds 50 valid cards.
5. These cards are used to purchase electronics from sites with poor security or are sold on forums for $10–$50 per card.

9. Ethical and legal aspects​

Card cracking is illegal in all countries and falls under criminal offenses related to cybercrime, fraud, and data theft. Punishments include fines, imprisonment, and confiscation of property.

From an ethical standpoint, card cracking harms not only the victims but also the entire online payment ecosystem, undermining trust in digital services.

10. Conclusion​

Brute-force card cracking is a complex and highly automated process that exploits weaknesses in online payment systems. It requires minimal initial data and can be performed with readily available tools, making it popular among cybercriminals. However, thanks to modern security methods (3D-Secure, anti-fraud systems, CAPTCHA) and user awareness, the risks can be significantly mitigated.

For educational purposes, it's important to understand how these attacks work in order to develop more robust security systems and educate users on online safety. If you'd like to delve deeper into a specific aspect (such as technical details of the tools or real-world attack examples), let me know, and I can provide additional information!