N10-005 · Question #298
A new firewall was recently installed blocking SMTP traffic. As a result, no one has Internet access. Which of the following has MOST likely occurred?
The correct answer is C. Implicit deny is blocking all traffic. Implicit deny is a fundamental firewall principle: any traffic not explicitly permitted by a rule is denied by default. When the new firewall was configured to block SMTP, it was likely set up with no other permit rules, meaning the implicit deny at the end of the rule set is…
Question
A new firewall was recently installed blocking SMTP traffic. As a result, no one has Internet access. Which of the following has MOST likely occurred?
Options
- APort security is blocking all traffic.
- BAn IDS is blocking all traffic.
- CImplicit deny is blocking all traffic.
- DSMTP is blocking all traffic.
How the community answered
(29 responses)- A3% (1)
- B7% (2)
- C86% (25)
- D3% (1)
Explanation
Implicit deny is a fundamental firewall principle: any traffic not explicitly permitted by a rule is denied by default. When the new firewall was configured to block SMTP, it was likely set up with no other permit rules, meaning the implicit deny at the end of the rule set is blocking all other traffic too - not just SMTP. This explains why no one has Internet access despite only SMTP being the intentional target. Port security (A) is a Layer 2 switch feature that limits MAC addresses on a port, not a firewall function. An IDS (B) detects intrusions but does not block traffic by itself (that's an IPS). SMTP itself (D) is an email protocol and cannot block all other Internet traffic.
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