The correct answer is that a polymorphic virus changes its code pattern every time it infects a new file or system. This mutation is its defining characteristic because it alters its own signature—often through encryption or variable instruction sequences—while preserving its core malicious functionality, specifically to evade signature-based detection tools used by antivirus software. On the Certified Ethical Hacker CEH exam, this concept tests your understanding of advanced evasion techniques; a common trap is confusing polymorphic viruses with metamorphic viruses, which rewrite their entire code rather than just mutating a decryption routine. Remember the memory tip: “Poly changes the lock, Meta changes the key”—polymorphic viruses change the appearance (the lock) but keep the same underlying payload (the key), forcing defenders to rely on behavior analysis rather than static signatures.
CEH Practice Question: Malware, Social Engineering and Network Attacks
This CEH practice question tests your understanding of malware, social engineering and network attacks. 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.
Which of the following is a characteristic of a polymorphic virus?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It changes its code pattern every time it infects a new file or system.
Polymorphic viruses mutate their code with each infection to evade signature-based detection, while often keeping the original functionality intact.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
It changes its code pattern every time it infects a new file or system.
Why this is correct
Polymorphic viruses use encryption or other techniques to change their signature while preserving functionality.
Related concept
Static NAT maps one inside address to one outside address.
✗
It spreads through network shares without requiring user interaction.
Why it's wrong here
This describes a worm, not a polymorphic virus.
✗
It remains dormant until a specific date or time.
Why it's wrong here
This describes a logic bomb or time bomb, not polymorphism.
✗
It infects the master boot record of a hard drive.
Why it's wrong here
This describes a boot sector virus, not necessarily polymorphic.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CEH NAT questions on configuration and troubleshooting.
Malware, Social Engineering and Network Attacks — This question tests Malware, Social Engineering and Network Attacks — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: It changes its code pattern every time it infects a new file or system. — Polymorphic viruses mutate their code with each infection to evade signature-based detection, while often keeping the original functionality intact.
What should I do if I get this CEH question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CEH NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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. Which of the following is a characteristic of a polymorphic virus?
easy
✓ A.It changes its code pattern with each infection to evade detection
B.It remains dormant until a specific date
C.It spreads without user interaction
D.It attaches to the boot sector of a hard drive
Why A: Polymorphic viruses change their code signature each time they replicate, making signature-based detection difficult.
Variation 2. Which TWO of the following are characteristics of a polymorphic virus? (Choose two.)
medium
A.It requires user interaction to activate
✓ B.It uses encryption to hide its payload
C.It infects only the boot sector
D.It spreads via email attachments only
✓ E.It changes its code signature each time it replicates
Why B: Polymorphic viruses mutate their code to evade signature detection while retaining functionality.
Variation 3. Which TWO of the following are characteristics of a polymorphic virus? (Choose 2)
medium
A.It does not require a host file to spread
✓ B.It changes its code signature each time it replicates
✓ C.It uses a mutation engine to generate new decryption routines
D.It only infects the master boot record
E.It attaches to email messages automatically
Why B: Polymorphic viruses change their code signature each time they replicate, using mutation engines to evade signature detection.
Variation 4. Which TWO of the following are characteristics of a polymorphic virus? (Select 2)
medium
A.It spreads without user interaction.
B.It attaches to a host file and does not change.
✓ C.It changes its code signature on each infection.
✓ D.It uses encryption to hide its payload.
E.It only infects the boot sector.
Why C: Polymorphic viruses change their code signature each time they replicate, making detection difficult. They often use encryption to hide malicious code.
Variation 5. Which TWO of the following are characteristics of a polymorphic virus? (Select 2)
medium
A.It spreads via email attachments only
✓ B.It changes its code signature each time it replicates
C.It requires a host file to attach
D.It self-replicates without user interaction
✓ E.It uses encryption to hide its payload
Why B: Polymorphic viruses change their code with each infection to evade signature detection, and they use encryption or mutation engines.
Variation 6. Which TWO of the following are characteristics of a polymorphic virus?
medium
✓ A.It changes its code signature each time it infects a new file
B.It spreads via email attachments
✓ C.It uses encryption with a variable key
D.It remains dormant until a specific date or time
E.It can infect the Master Boot Record (MBR)
Why A: Option A is correct because a polymorphic virus changes its decryption routine and code signature each time it infects a new file, making signature-based detection difficult. This mutation is achieved by using a polymorphic engine that generates varied decryption loops while preserving the malicious payload.
Variation 7. Which TWO of the following are characteristics of a polymorphic virus?
medium
✓ A.It uses a decryption routine that varies
B.It uses a constant signature across all infections
✓ C.It changes its code signature each time it replicates
D.It can only infect boot sectors
E.It always remains in memory
Why A: A polymorphic virus changes its code signature (using encryption/decryption) each time it replicates to evade signature-based detection, while retaining its functionality.
Variation 8. Which type of malware is characterized by modifying its own code to evade signature-based detection, often changing its appearance each time it replicates?
medium
✓ A.Polymorphic virus
B.Trojan horse
C.Macro virus
D.Boot sector virus
Why A: Polymorphic malware changes its code (but retains functionality) to avoid detection by signature-based antivirus.
Last reviewed: Jun 21, 2026
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This CEH 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 CEH exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.