The answer is signed malware, which represents a threat where a file carries a valid digital signature from a trusted vendor but executes malicious code. This scenario is correct because the digital certificate used to sign the file has likely been compromised—either stolen from the vendor, misused by an insider, or issued fraudulently by a rogue certificate authority. The trusted signature bypasses reputation-based defenses and application allowlists, making the threat especially insidious since security tools that trust the vendor’s certificate will treat the file as legitimate. On the CISA exam, this concept tests your understanding of certificate lifecycle risks and the limits of signature-based validation; a common trap is confusing signed malware with a simple virus or trojan that lacks a valid signature. Remember the key distinction: the certificate itself is valid, but the signer is not trustworthy. A useful memory tip is “trust the chain, not the file”—just because a signature is cryptographically valid does not mean the software is safe.
CISA Protection of Information Assets Practice Question
This CISA practice question tests your understanding of protection of information assets. 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.
A company's endpoint protection solution alerts on a file that is digitally signed by a trusted software vendor but exhibits malicious behavior on execution. What type of threat does this scenario most likely depict?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Signed malware, indicating the certificate may have been compromised.
The scenario describes a file that is digitally signed by a trusted vendor yet exhibits malicious behavior. This is the classic definition of signed malware, where the digital certificate used to sign the file has likely been stolen, misused, or issued fraudulently. The trusted signature bypasses reputation-based and allowlist controls, making the threat particularly dangerous because the file appears legitimate to security tools that trust the vendor's certificate.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 Trojan horse disguised as legitimate software.
Why it's wrong here
Trojans are malware that appear legitimate but may not be signed; the distinguishing factor here is the valid signature.
✓
Signed malware, indicating the certificate may have been compromised.
Why this is correct
The file has a trusted digital signature but performs malicious actions, suggesting the signing key was stolen or misused.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
A zero-day exploit targeting an unpatched vulnerability.
Why it's wrong here
The file's behavior is malicious, but the key aspect is its legitimate digital signature; zero-day focuses on unknown vulnerabilities.
✗
A fileless attack that never writes to disk.
Why it's wrong here
Fileless attacks reside in memory; this scenario involves a file with a digital signature.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse 'signed malware' with a 'Trojan horse,' but the critical differentiator is the presence of a valid digital signature from a trusted vendor, which is not inherent to Trojans and is the specific mechanism that makes this threat unique.
Trap categories for this question
Scenario analysis trap
Fileless attacks reside in memory; this scenario involves a file with a digital signature.
Detailed technical explanation
How to think about this question
Signed malware exploits the trust chain of code signing certificates. Attackers may steal the private key from a vendor's build server, purchase a certificate from a compromised certificate authority (CA), or trick a CA into issuing a certificate for a malicious executable. Once signed, the file can bypass Windows Defender SmartScreen, AppLocker, and many antivirus engines that trust the vendor's root certificate, allowing the malware to execute without triggering signature-based alerts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Protection of Information Assets — This question tests Protection of Information Assets — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Signed malware, indicating the certificate may have been compromised. — The scenario describes a file that is digitally signed by a trusted vendor yet exhibits malicious behavior. This is the classic definition of signed malware, where the digital certificate used to sign the file has likely been stolen, misused, or issued fraudulently. The trusted signature bypasses reputation-based and allowlist controls, making the threat particularly dangerous because the file appears legitimate to security tools that trust the vendor's certificate.
What should I do if I get this CISA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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