Selecting IoCs from Dynamic Malware Analysis for Threat Intelligence
During dynamic analysis of a malware sample in a sandbox, an analyst observes the following behaviours: (1) A file is created at C:\Windows\System32\drivers\etc\hosts, (2) A registry key is set at HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\UpdateSvc, (3) Outbound TCP connections to 198.51.100.10 on port 8080. Which THREE of the following IoCs are MOST relevant to share with the threat intelligence team?
Quick Answer
The answer is the registry key HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\UpdateSvc, because persistence mechanisms are the most critical indicators of compromise to share when performing dynamic analysis for threat intelligence. While the outbound TCP connection to 198.51.100.10 on port 8080 is a valuable network IoC, the registry Run key directly reveals how the malware achieves autorun persistence, enabling the threat intelligence team to detect and remove the threat across endpoints. On the CHFI exam, this question tests your ability to prioritize IoCs that provide long-term detection value over transient network artifacts, as persistence indicators are more stable and less likely to change than IP addresses. A common trap is selecting the hosts file modification, which is often overwritten by security software, or the IP address, which may be rotated by attackers. Memory tip: think "Persistence First" — always prioritize registry Run keys, scheduled tasks, or service installations over network connections when asked for the most relevant IoCs from dynamic analysis.
⚠ Common exam trap
EC-Council often tests the distinction between observed behaviors (file creation, registry modification, network connections) and derived IoCs (hashes, mutexes), tricking candidates into selecting all listed options rather than only those directly tied to the observed actions.
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
✓
Network connection to 198.51.100.10:8080
The outbound TCP connection to 198.51.100.10 on port 8080 is a direct network-based indicator of compromise (IoC) that threat intelligence teams can use to block or monitor malicious C2 traffic. This IP and port combination represents a specific command-and-control endpoint, making it highly actionable for network defense and threat hunting.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
MD5 hash of the original malware file
Why it's wrong here
While hashes are useful, the question asks for the MOST relevant based on observed behaviours; the file hash is not described in the observation.
- ✓
Network connection to 198.51.100.10:8080
Why this is correct
This is a network-based IoC indicating C2.
- ✓
Registry key HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\UpdateSvc
Why this is correct
Persistence via Run key.
- ✗
Mutex name created by the malware
Why it's wrong here
Mutex is not mentioned in the observed behaviours.
- ✓
File path C:\Windows\System32\drivers\etc\hosts
Why this is correct
Hosts file modification is a common technique for DNS poisoning or blocking.
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Same concept, more angles
2 more ways this is tested on CHFI
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. During dynamic analysis of a malware sample, an analyst observes the following: creation of a mutex named `Global\{9A2D7E1C-3F4B-4A5E-9B8C-1D2E3F4A5B6C}`, a registry key under `HKCU\Software\Microsoft\Windows\CurrentVersion\Run` named `WindowsUpdate`, and outbound TCP traffic to `203.0.113.5:443`. Which THREE of the following indicators of compromise (IoCs) should be documented?
hard- ✓ A.Outbound TCP to `203.0.113.5:443`
- B.SHA256 hash of the malware sample
- ✓ C.Mutex name `Global\{9A2D7E1C-3F4B-4A5E-9B8C-1D2E3F4A5B6C}`
- D.File path `C:\Windows\System32\notepad.exe`
- ✓ E.Registry key `HKCU\...\Run\WindowsUpdate`
Why A: Outbound TCP traffic to a specific IP address and port (203.0.113.5:443) is a classic network-based indicator of compromise (IoC). During dynamic analysis, this demonstrates the malware's command-and-control (C2) communication, often using HTTPS over port 443 to blend with legitimate traffic. Documenting this IoC allows defenders to block the endpoint and detect similar infections via network monitoring.
Variation 2. A security analyst runs a dynamic analysis of a suspected malware sample using Cuckoo Sandbox. The report shows that the sample created a mutex named 'Global\MyMaliciousMutex', added a registry run key under HKCU\Software\Microsoft\Windows\CurrentVersion\Run, and attempted to communicate with an IP address 185.10.68.12 on port 443. Which of the following is the BEST immediate indicator of compromise (IoC) to share with the threat intelligence team?
hard- A.The registry run key location
- B.The sample's MD5 hash
- ✓ C.The IP address 185.10.68.12
- D.The mutex name 'Global\MyMaliciousMutex'
Why C: The IP address 185.10.68.12 on port 443 is the best immediate indicator of compromise (IoC) because it is a network-based artifact that can be directly blocked at the firewall or monitored for outbound connections. Network-based IoCs are often prioritized in threat intelligence sharing because they enable proactive perimeter defense and are actionable across multiple systems, unlike host-based artifacts (mutexes, registry keys) that require endpoint-level detection. Additionally, the IP address is independent of file hashes and can be used to detect or block communications even when the malware binary changes.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CHFI practice question is part of Courseiva's free EC-Council 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 CHFI exam.