mediumMultiple Choice
200-201 Practice Question: A network administrator configures an IPS to drop…
A network administrator configures an IPS to drop packets that match a signature for SQL injection. However, legitimate web traffic is being blocked. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the distinction between false positives and false negatives, and the trap here is that candidates may confuse 'blocking legitimate traffic' with a false negative, not realizing that a false positive is the correct term for incorrectly flagged benign traffic.
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
✓
Signature false positive
A false positive occurs when the IPS incorrectly identifies legitimate traffic as malicious based on its signature. In this case, the SQL injection signature is matching benign web requests that contain patterns resembling SQL syntax (e.g., 'SELECT', 'DROP'), causing the IPS to drop valid packets. This is a common issue with signature-based detection systems that lack contextual analysis.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
IPS hardware failure
Why it's wrong here
Hardware failure would halt all inspection or cause the sensor to fail open or closed, not selectively drop traffic matching one SQL injection signature. Hardware replacement is the right response when the appliance itself is down, but here the signature is matching legitimate requests, indicating a false positive.
- ✗
Network congestion
Why it's wrong here
Congestion delays or drops packets indiscriminately across all flows, not only those matching the SQL injection signature. Bandwidth upgrades or QoS are correct when throughput is the bottleneck, but legitimate web traffic being blocked by a specific signature points to signature tuning, not link saturation.
- ✓
Signature false positive
Why this is correct
A signature false positive occurs when legitimate traffic matches an attack pattern the IPS was not designed to see in that context. Here, benign web requests containing SQL-like strings trigger the SQL injection signature, causing the IPS to drop them. This directly explains the over-blocking of legitimate web traffic described in the stem.
- ✗
Signature false negative
Why it's wrong here
A false negative means malicious traffic passes uninspected; the stem describes legitimate traffic being blocked, which is a false positive. False negatives are addressed by adding or tightening signatures, whereas here the SQL injection signature is over-matching benign requests and needs tuning or exception rules.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-201 practice question is part of Courseiva's free Cisco 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 200-201 exam.