CISM Information Security Program Practice Question
Exhibit
Refer to the exhibit. Exhibit: ``` access-list 100 deny ip any 10.0.0.0 0.255.255.255 access-list 100 permit tcp 192.168.1.0 0.0.0.255 host 10.0.0.5 eq 80 access-list 100 deny ip any any ``` The ACL is applied inbound on the external interface of the border router.
Based on the exhibit, which of the following is true about traffic from the internet to the internal network 10.0.0.0/8?
⚠ Common exam trap
The trap here is that candidates often misread the direction of the ACL permit statement (10.0.0.0/8 to 192.168.1.0/24) and incorrectly assume it permits traffic from the internet to the internal network, when in fact it only permits outbound traffic from the internal network to the specified destination.
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
✓
All traffic from the internet to the internal network is denied.
The exhibit shows an access control list (ACL) that denies all traffic from any source to the 10.0.0.0/8 network. Since the ACL is applied inbound on the internet-facing interface, any traffic originating from the internet destined for the internal network 10.0.0.0/8 is implicitly denied by the explicit deny statement. Therefore, option B is correct: all traffic from the internet to the internal network is denied.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Internet traffic to 10.0.0.5 is permitted only if from 192.168.1.0/24.
Why it's wrong here
The deny rule blocks all, and source 192.168.1.0/24 is internal, not internet.
- ✓
All traffic from the internet to the internal network is denied.
Why this is correct
First rule denies all IP traffic to 10.0.0.0/8.
- ✗
Traffic from the internet to 10.0.0.5 port 80 is permitted.
Why it's wrong here
The earlier deny rule blocks all traffic to 10.0.0.0/8; permit is never evaluated.
- ✗
Traffic from 192.168.1.0/24 to 10.0.0.5 port 80 is permitted.
Why it's wrong here
That source is internal; ACL on external interface doesn't apply to internal traffic.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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