PCNSA Decryption and Monitoring Practice Question
After enabling SSL decryption, users report that some websites fail to load. The firewall logs show 'decryption error' for these sites. Which decryption profile setting should the administrator check first?
⚠ Common exam trap
Watch out — candidates often confuse 'untrusted issuer' with 'expired certificate' or 'certificate status unknown', but the 'decryption error' log specifically points to a chain-of-trust validation failure, which is directly controlled by the 'Block sessions with untrusted issuers' setting.
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
✓
Block sessions with untrusted issuers
When SSL decryption is enabled, the firewall acts as a man-in-the-middle and must re-sign the server's certificate with its own CA. If the server's certificate is issued by an untrusted CA (i.e., not in the firewall's trusted CA list), the firewall cannot verify the chain of trust and will block the session if the 'Block sessions with untrusted issuers' option is enabled. This is the most common cause of 'decryption error' logs for sites that previously worked without decryption.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Block sessions with expired certificates
Why it's wrong here
Expired certificates also cause errors, but untrusted issuers are a more common first check.
- ✗
Block sessions with certificate status unknown
Why it's wrong here
This setting depends on CRL/OCSP; it is less likely to be the first cause.
- ✗
Block sessions with unsupported cipher suites
Why it's wrong here
Unsupported ciphers cause a different failure, not typically logged as 'decryption error'.
- ✓
Block sessions with untrusted issuers
Why this is correct
If enabled, sessions with certificates from untrusted CAs will be blocked, causing 'decryption error'.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCNSA practice question is part of Courseiva's free Palo Alto Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNSA exam.