200-201 Security Monitoring Practice Question
An analyst is reviewing IDS alerts and sees an alert with signature name 'ET POLICY Suspicious inbound to MySQL port 3306'. The source IP is external and destination is an internal database server. What is the best immediate action?
⚠ Common exam trap
Cisco often tests the misconception that IDS alerts should be analyzed for false positives before taking action, but in this scenario, the immediate risk of an external connection to a database port demands a blocking response first, with analysis to follow.
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 the external IP at the firewall
An inbound connection from an external IP to a MySQL server (port 3306) is highly suspicious — MySQL is a database service that should never be exposed directly to the internet. The immediate best action is to block the external IP at the firewall to prevent potential exploitation, data exfiltration, or brute-force attacks. This aligns with the principle of least privilege and defense-in-depth, as database servers should only accept connections from trusted internal hosts.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Allow the traffic because it is a legitimate database query
Why it's wrong here
Inbound MySQL from an external source to an internal database server violates the expected trust boundary; legitimate queries would originate from the application tier, not the internet. Permitting it exposes the database to exploitation. It is tempting because port 3306 traffic is normal in application environments, but only when sourced internally.
- ✗
Ignore the alert as it is a false positive
Why it's wrong here
Dismissing the alert as a false positive ignores that external-to-internal MySQL traffic breaches the expected trust boundary and warrants investigation, not assumption. It is tempting because ET POLICY signatures can be noisy, but that label indicates policy violation detection, which is precisely what this scenario describes.
- ✗
Disable the signature to reduce noise
Why it's wrong here
Disabling the signature removes detection of external access attempts to MySQL, leaving the database server blind to the very reconnaissance and exploitation traffic the IDS exists to catch. It is tempting when alert volume is high, but signature tuning or suppression for known-good internal hosts is the correct noise-reduction approach.
- ✓
Block the external IP at the firewall
Why this is correct
Blocking the external source at the firewall immediately stops further inbound attempts to the MySQL port, containing the threat while investigation proceeds. This satisfies the need for the fastest containment action against a confirmed external probe of an internal database.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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