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ISC2 CC Practice Question: During a security audit, you discover that a…
During a security audit, you discover that a financial application stores passwords using MD5 hashing without salt. What is the primary security concern with this practice?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Without salting, the hashes are vulnerable to precomputed rainbow table attacks
MD5 is a fast hash, making it susceptible to brute-force and rainbow table attacks. Without salting, identical passwords produce identical hashes, allowing precomputed rainbow tables to quickly reverse them. Hashing is one-way, so MD5 is not reversible in the true sense. Speed is a vulnerability, not a benefit. Compliance is secondary but not the primary security concern.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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MD5 is reversible, allowing attackers to recover plaintext passwords
Why it's wrong here
MD5 is a one-way cryptographic hash, not encryption, so plaintext cannot be recovered by reversing it. The real weakness is collision resistance and speed, which permit brute-force and rainbow-table cracking of unsalted digests. Reversibility describes encoding or encryption, not hashing.
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MD5 is too slow, causing performance issues during authentication
Why it's wrong here
MD5 is a fast hash, which is the problem: high throughput lets attackers test billions of candidate passwords per second against stolen digests. Performance during authentication is not the concern. Slow hashing is deliberately chosen in password schemes such as bcrypt to hinder cracking.
- ✓
Without salting, the hashes are vulnerable to precomputed rainbow table attacks
Why this is correct
Unsalted MD5 lets attackers hash every candidate password once and reuse the resulting lookup table across all accounts. Rainbow tables exploit this by trading precomputation for fast cracking, so identical passwords yield identical hashes, undermining the credential store's resistance to offline attack.
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Storing hashes violates PCI DSS compliance, but does not affect security
Why it's wrong here
Unsalted MD5 enables precomputed rainbow-table and brute-force attacks, so security is directly undermined; PCI DSS also requires strong cryptography for stored cardholder data. The option wrongly severs compliance from security. Compliance mandates exist precisely because weak hashing exposes credentials.
Go deeper
Related to this question
Learn chapter
Security Governance and Compliance
Key term
General Data Protection Regulation
A European Union law that gives individuals control over their personal data and sets strict rules for how organizations collect, store, and process that data.
Key term
Vulnerability
A vulnerability is a weakness in a system, network, or software that could be exploited by a threat to cause harm or unauthorized access.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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