Which data transfer protocols (e.g. HTTP vs. HTTPS) are most vulnerable to card information interception?

[Student]

Introduction to Data Transfer Protocols and Their Vulnerabilities​

Data transfer protocols are a set of rules that define how information is exchanged between devices on a network such as the internet. They are used in a variety of applications, from websites to email and file transfers. When transmitting sensitive information like credit card data (card number, CVV, expiration date), encryption —the process of making the data unreadable to outsiders—is key. Without encryption, data is transmitted in plaintext, making it vulnerable to eavesdropping or man-in-the-middle (MITM) attacks.

In this answer, I'll discuss the most common protocols, their operating mechanisms, vulnerabilities, and attack examples. We'll focus on HTTP and HTTPS as the examples in your question, but we'll also touch on other protocols for completeness. The goal is educational: to understand why some protocols are secure and others are not, and how this impacts real-world scenarios. I'll structure the material step by step, with examples and recommendations.

1. Basic Concepts: Data Interception and Why It's Possible​

• Data eavesdropping: This is when an attacker "eavesdrops" on traffic between a sender (e.g., your browser) and a recipient (a server). On unsecured networks, such as public Wi-Fi, this can be done using tools like Wireshark or tcpdump.
• Man-in-the-Middle (MITM): An attacker inserts himself between the parties, intercepting and possibly modifying data. Without encryption, this is trivial; with encryption, it's more difficult, but possible given weaknesses.
• Card data: According to the PCI DSS (Payment Card Industry Data Security Standard), card data must be transmitted only over secure channels. A breach could result in identity theft, financial losses, and legal consequences.

Unencrypted protocols (such as HTTP) are the most vulnerable because the data is visible as is. Encrypted protocols (such as HTTPS) protect it, but are not perfect.

2. HTTP: The most vulnerable protocol for interception​

HTTP (HyperText Transfer Protocol) is the basic protocol for web pages, developed in 1991. It runs on port 80 and transfers data in plaintext.

• How it works:
  1. The client (browser) sends a request (GET or POST) to the server.
  2. The server responds with data.
  3. All data – text, images, forms – are transmitted without protection.
• Vulnerabilities for interception of card data:
  • Lack of encryption: Card details entered into the payment form are visible in the data packet. An attacker can intercept them online.
  • Examples of attacks:
    • Sniffing: On a local area network (LAN) or Wi-Fi, an attacker uses ARP spoofing to redirect traffic through themselves and read the data.
    • Passive interception: Simply monitoring traffic without intervention. For example, if you enter card details on http://example.com/pay , the card number is visible in the POST request: card_number=1234567890123456&cvv=123.
  • Risks: High. According to reports (such as Verizon DBIR), insecure protocols are responsible for many data theft incidents. In the 2020s, HTTP was deprecated for sensitive data, and browsers (Chrome, Firefox) warn of its insecurity.
• Why it's most vulnerable: There's no server authentication or encryption. Anyone in the chain (ISP, router) can see the data.

3. HTTPS: More secure, but not without vulnerabilities​

HTTPS (HTTP Secure) is HTTP with added encryption via TLS (Transport Layer Security, formerly SSL). It runs on port 443.

• How it works(educational analysis of the process):
  1. TLS Handshake:
     • The client requests a connection.
     • The server provides a certificate (issued by a certificate authority, CA, such as Let's Encrypt).
     • The client checks the certificate (validity, expiration, matches the domain).
     • The parties agree on encryption keys (using asymmetric encryption, such as RSA or ECDHE).
     • Data is encrypted with a symmetric key (e.g. AES-256).
  2. Data transmission: Everything, including card data, is encrypted. An attacker only sees encrypted traffic.
• Vulnerabilities for interception of card data:
  • Weak TLS versions: TLS 1.0/1.1 are deprecated and have vulnerabilities (for example, the POODLE attack, where an attacker forces a downgrade to SSLv3 and decrypts). TLS 1.2+ or 1.3 (the standard since 2018) is recommended.
  • Problems with certificates:
    • Self-signed certificates: Not trusted, browser warns, but if user ignores, MITM is possible.
    • CA Compromise: Rare, but if a hacker issues a fake certificate (like the DigiNotar case in 2011), they can spoof the server.
  • Downgrade attacks: An attacker forces the connection to fall back to HTTP (for example, through SSL stripping). Protection: HSTS (HTTP Strict Transport Security) is a header that forces the browser to always use HTTPS.
  • Side-channel attacks: Rare, but possible (e.g. Heartbleed in OpenSSL 2014, where a memory leak allowed keys to be read).
  • Phishing: Sites with HTTPS (green lock) appear secure, but if they are fake (such as a homograph attack with a look-alike domain), card details can be stolen.
  • Attack examples: In 2023, attacks on weak TLS led to data breaches at companies like Equifax. However, HTTPS reduces the risk by 99% compared to HTTP.
• Why it's safer: Encryption makes interception useless without keys. Server authentication prevents spoofing.

4. Other protocols and their vulnerabilities​

For completeness, let's look at the protocols that can be used to transfer card data (for example, via email or files):

• FTP (File Transfer Protocol):
  • Works in plaintext (port 21).
  • Vulnerability: Full, like HTTP. Card data in files (e.g., CSV files with payments) can be easily intercepted.
  • Alternative: FTPS (FTP over TLS) or SFTP (SSH File Transfer Protocol) - with encryption.
• SMTP (Simple Mail Transfer Protocol):
  • For email (port 25/587).
  • Vulnerability: Without STARTTLS, data (including cards in emails) is in plaintext. Many servers still don't use TLS.
  • Risks: Interception in transit. Recommendation: Use SMTPS or email with end-to-end encryption (PGP).
• Telnet:
  • Deprecated for remote access.
  • Vulnerability: Completely open. Do not use for sensitive data. Alternative: SSH (Secure Shell) with encryption.
• WebSockets (ws:// vs wss://):
  • For real time (chats, payments).
  • ws:// — like HTTP, vulnerable. wss:// — like HTTPS, secure.
• Comparison table of vulnerabilities:

Protocol	Encryption	Vulnerability to interception	Examples of use	Recommendation
HTTP	No	High (plaintext)	Old sites	Avoid for cards
HTTPS	Yes (TLS)	Low, but possible in case of weaknesses	Modern payments	Standard; use TLS 1.3
FTP	No	High	File transfers	Replace with SFTP/FTPS
SMTP	Optional (STARTTLS)	Average	Email	Always with TLS
Telnet	No	High	Remote access	Replace with SSH

5. Educational recommendations and best practices​

• Avoid vulnerable protocols: Never transmit card data over HTTP, FTP, or unsecured SMTP. Use HTTPS at a minimum.
• Additional measures:
  • Tokenization: Instead of handing over the full card, use tokens (such as those from Stripe or PayPal).
  • VPN: Encrypts all traffic, protecting you even on unsecured networks.
  • Monitoring: Use tools like OWASP ZAP to test for vulnerabilities.
  • Updates: Keep TLS up to date; browsers automatically block older versions.
• Real-world examples: In 2017, the Equifax breach (143 million records, including cards) occurred due to vulnerabilities in a web application without proper encryption.
• For developers: Implement Content Security Policy (CSP) and check for OWASP Top 10 vulnerabilities.

Conclusion​

HTTP and similar unsecured protocols (FTP, Telnet) are most vulnerable to card data interception due to the lack of encryption. HTTPS significantly reduces risks thanks to TLS, but requires proper configuration. For educational purposes, remember: security is a multi-layered approach. If you're developing a system, study PCI DSS and conduct audits. If you have specific scenarios (such as mobile apps), inquire about more targeted advice.