The Evolution of Cisco Passwords: From Plaintext to Scrypt

Understanding the evolution of Cisco password types is essential for protecting your network infrastructure from unauthorized access. Over the years, Cisco has introduced different password algorithms, each with varying levels of security. Some are relics of the past, while others are modern standards designed to withstand today’s sophisticated attacks.

Imagine auditing a Cisco router configuration and discovering a password in clear text — this scenario still happens more often than you might think. Knowing which password types to use and which to retire is key to maintaining a secure network.

1. Type 0: Plaintext (Obsolete)

Type 0 passwords are exactly what they sound like — plain text with no encryption. Any user with access to the configuration file can read them immediately. This method offers zero protection and is extremely risky in any production environment.

Key takeaway: Type 0 should never be used.

2. Type 7: Vigenère Cipher (Obsolete)

Introduced as a way to obscure passwords from casual observers, Type 7 uses a simple Vigenère cipher, essentially a basic alphabetical substitution. Unfortunately, this cipher is fully reversible, and anyone with basic tools can decode the password in seconds.

Key takeaway: Treat Type 7 as obfuscated, not secure, and avoid it in production.

3. Type 4: Flawed SHA-256 (Deprecated)

Type 4 was Cisco’s 2013 attempt to implement PBKDF2 hashing but suffered from a serious flaw — it performed only a single iteration of SHA-256 without a salt, making it weaker than even Type 5. Due to this vulnerability, Type 4 was quickly deprecated.

Key takeaway: Type 4 is no longer recommended.

4. Type 5: MD5 Salted (Legacy)

Type 5 passwords use salted MD5 hashing with 1,000 iterations. For decades, this was the standard for securing Cisco devices. However, with modern GPU-based cracking tools, it is relatively easy to attack. While stronger than Type 7, Type 5 is considered legacy and should only be used if your hardware does not support newer types.

Key takeaway: Type 5 is legacy only, consider upgrading if possible.

5. Type 8: PBKDF2-HMAC-SHA256 (Secure)

Type 8 fixed the flaws of Type 4, implementing PBKDF2 with SHA-256, a 10-character (80-bit) salt, and 20,000 iterations. This makes brute-force attacks much more difficult, and it is considered secure for modern deployments.

Key takeaway: Type 8 is recommended for most networks.

6. Type 9: Scrypt (Best Practice)

The current gold standard is Type 9, which uses the scrypt algorithm. Scrypt is memory-hard, meaning it requires significant memory to calculate, which drastically increases the cost of brute-force attacks, even on large GPU clusters.

Key takeaway: Type 9 represents best practice for Cisco password security.

Summary of Cisco Password Types

Security Best Practices

1. Retire legacy passwords: Remove Type 0, Type 7, and Type 4 lines from your configuration.
2. Use modern secrets: Use enable secret commands with Type 8 or Type 9 wherever supported.
3. Enforce strong passwords: Require at least 15 alphanumeric characters with a mix of upper/lowercase and symbols.
4. Regular audits: Periodically review your device configurations to ensure no weak or outdated passwords remain.

By following these best practices, network administrators can protect their Cisco infrastructure against unauthorized access, ensuring the network remains both reliable and secure.