CEH Practice Question: Malware, Social Engineering and Network Attacks
During a forensic investigation, an analyst finds a suspicious file that changes its code signature each time it replicates. The file uses encryption and polymorphism to evade signature-based detection. Which type of virus is this?
⚠ Common exam trap
CEH often tests the distinction between a polymorphic virus and a metamorphic virus; the trap here is that candidates may confuse 'polymorphic' (which changes the decryption routine but keeps the body encrypted) with 'metamorphic' (which rewrites its entire code without encryption), but the question explicitly mentions encryption, confirming polymorphism.
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
✓
Polymorphic virus
D is correct because a polymorphic virus is specifically designed to change its code signature each time it replicates, using encryption and mutation engines to evade signature-based detection. The description of altering the signature with each replication while maintaining the same core functionality is the defining characteristic of a polymorphic virus.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Macro virus
Why it's wrong here
Macro viruses embed malicious code within document macros, primarily targeting data files like Microsoft Word or Excel documents. They execute when the document is opened and macros are enabled, leveraging the application's scripting capabilities. Unlike polymorphic viruses, their code typically remains static and in plain text within the macro language, making them detectable by consistent signatures rather than requiring mutation.
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File infector virus
Why it's wrong here
File infector viruses attach their malicious code directly to legitimate executable files, such as .EXE or .COM files, modifying them to execute the virus whenever the host program runs. While some advanced file infectors can incorporate polymorphic capabilities, the term itself refers solely to their method of infection—modifying program files—not necessarily their ability to mutate their code signature. Many file infectors are non-polymorphic, relying on simple appending or prepending techniques.
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Boot sector virus
Why it's wrong here
Boot sector viruses infect the Master Boot Record (MBR) or Volume Boot Record (VBR) of storage devices, executing during the system's initial startup sequence before the operating system fully loads. Due to the critical and space-constrained nature of boot sectors, these viruses typically have a very small footprint and rarely incorporate complex polymorphic engines. Their primary evasion technique relies on early execution and low-level system control rather than code mutation.
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Polymorphic virus
Why this is correct
Polymorphic viruses are a sophisticated type of malware designed to evade signature-based detection by constantly changing their executable code while retaining their original functionality. They achieve this through a 'mutation engine' that encrypts the virus body with a different key and decryption routine for each new infection. This process ensures that every new instance of the virus has a unique signature, making it extremely challenging for traditional antivirus software to identify based on static patterns.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.