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ISC2 CC Practice Question: A security analyst reviews this firewall log entry
Exhibit
Refer to the exhibit. ``` Jul 15 09:32:17 firewall kernel: [429493.77] IN=eth0 OUT= MAC=00:1a:2b:3c:4d:5e:00:11:22:33:44:55:08:00 SRC=203.0.113.5 DST=198.51.100.20 LEN=40 TOS=0x00 PREC=0x00 TTL=64 ID=54321 PROTO=TCP SPT=44523 DPT=445 WINDOW=1024 RES=0x00 SYN URGP=0 ```
A security analyst reviews this firewall log entry. What type of activity is most likely being attempted?
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 potential SMB exploitation attempt from an external host.
The log shows a TCP SYN packet from a high source port to destination port 445 (SMB), commonly used in ransomware attacks like EternalBlue.
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 legitimate SMB file sharing connection from an internal client.
Why it's wrong here
The source IP is external (203.0.113.5) and the destination is internal (198.51.100.20), indicating an inbound connection attempt.
- ✓
A potential SMB exploitation attempt from an external host.
Why this is correct
The SYN packet to port 445 from an external source is typical of SMB exploits such as EternalBlue.
- ✗
A port scan attempt on port 445.
Why it's wrong here
A single SYN packet does not indicate a scan; scans usually have multiple packets.
- ✗
An outbound connection to an SMB server.
Why it's wrong here
The destination is internal, so it's inbound, not outbound.
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Related to this question
Learn chapter
Introduction to Security Principles
Key term
TCP
TCP is a connection-oriented transport layer protocol that ensures reliable, ordered, and error-checked delivery of data between applications over IP networks.
Key term
Firewall
A firewall is a network security system that monitors and controls incoming and outgoing traffic based on predetermined security rules to protect trusted internal networks from untrusted external networks.
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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.