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ISC2 CC Practice Question: An analyst reviews the firewall log exhibit

Exhibit

Refer to the exhibit.

```
EdgeRouter# show firewall log
Log for firewall-in
Fri Aug 18 14:23:45 2023 : IN=eth0 OUT=eth1 MAC=00:1a:2b:3c:4d:5e:6f:7a:8b:9c:0d:1e:2f SRC=10.0.1.100 DST=203.0.113.50 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=12345 DF PROTO=TCP SPT=34567 DPT=80 WINDOW=65535 RES=0x00 SYN URGP=0
Fri Aug 18 14:23:46 2023 : IN=eth0 OUT=eth1 MAC=00:1a:2b:3c:4d:5e:6f:7a:8b:9c:0d:1e:2f SRC=10.0.1.100 DST=203.0.113.50 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=12346 DF PROTO=TCP SPT=34568 DPT=80 WINDOW=65535 RES=0x00 SYN URGP=0
Fri Aug 18 14:23:47 2023 : IN=eth0 OUT=eth1 MAC=00:1a:2b:3c:4d:5e:6f:7a:8b:9c:0d:1e:2f SRC=10.0.1.100 DST=203.0.113.50 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=12347 DF PROTO=TCP SPT=34569 DPT=80 WINDOW=65535 RES=0x00 SYN URGP=0
```

An analyst reviews the firewall log exhibit. The source IP 10.0.1.100 is an internal web server. The destination IP 203.0.113.50 is an external host. What does this log pattern MOST likely indicate?

⚠ Common exam trap

ISC2 often tests the candidate's ability to interpret traffic direction and normal vs. anomalous behavior, and the trap here is assuming that any traffic from a web server is legitimate, ignoring that internal servers should not typically initiate outbound connections to external hosts.

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

✓

A denial-of-service (DoS) attack from the internal server to the external host

The log pattern shows the internal web server (10.0.1.100) sending traffic to an external host (203.0.113.50). In a typical network, internal web servers serve content to internal users, not initiate outbound connections to external hosts. This anomalous outbound traffic pattern, especially if it involves a high volume of packets or connections, is characteristic of a denial-of-service (DoS) attack where the internal server is used as a source to flood the external target, potentially due to compromise or misconfiguration.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✓

    A denial-of-service (DoS) attack from the internal server to the external host

    Why this is correct

    Multiple SYN packets without completion indicate a SYN flood, a type of DoS attack.

  • ✗

    A port scan from the internal server to the external host

    Why it's wrong here

    A port scan would target multiple ports on the destination, but here only port 80 is used.

  • ✗

    Normal web traffic from the server to the external host

    Why it's wrong here

    Normal traffic would show SYN, SYN-ACK, ACK, not repeated SYNs.

  • ✗

    An attempted SQL injection attack from the external host to the internal server

    Why it's wrong here

    SQL injection involves application-layer payload, not just SYN packets; also the direction is internal to external.

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JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This CC practice question is part of Courseiva's free ISC2 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 CC exam.