This CAS-004 practice question tests your understanding of security operations. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A security analyst is conducting a penetration test for a client. The rules of engagement specify that no social engineering is allowed. Which TWO of the following reconnaissance techniques are permitted under these rules?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Scanning the client's external network for open ports
Passive reconnaissance (OSINT) does not interact with the target and is allowed. Active reconnaissance without social engineering is also typically allowed if specified. Social engineering involves human interaction, which is prohibited.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Calling the help desk to obtain credentials
Why it's wrong here
Calling is social engineering.
✓
Scanning the client's external network for open ports
Why this is correct
Port scanning is active recon but does not involve social engineering.
Related concept
Standard ACLs match source addresses.
✓
Performing DNS enumeration using public records
Why this is correct
DNS enumeration via public records is passive OSINT.
Related concept
Standard ACLs match source addresses.
✗
Sending phishing emails to employees
Why it's wrong here
Phishing is social engineering.
✗
Tailgating into the building
Why it's wrong here
Tailgating is physical social engineering.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related CAS-004 ACL questions on filtering logic and placement.
Security Operations — This question tests Security Operations — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Scanning the client's external network for open ports — Passive reconnaissance (OSINT) does not interact with the target and is allowed. Active reconnaissance without social engineering is also typically allowed if specified. Social engineering involves human interaction, which is prohibited.
What should I do if I get this CAS-004 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related CAS-004 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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