The answer is SUID abuse to read sensitive files, as the world-executable backup script running with root privileges due to the SUID bit allows any user to bypass normal file permissions and access /etc/shadow. This is correct because the script, owned by root and set with the SUID bit, executes with the owner’s elevated privileges, enabling it to read the root-only shadow file and write password hashes to a world-readable location—a classic privilege escalation path. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of Linux permission misconfigurations and how attackers exploit SUID binaries to exfiltrate sensitive data; a common trap is assuming the script itself must be malicious, when in fact the SUID bit on any root-owned executable that accesses restricted files is the vulnerability. Remember the mnemonic: SUID scripts that touch shadow are a shortcut to root—always check what the binary reads and writes.
CEH Enumeration and System Hacking Practice Question
This CEH practice question tests your understanding of enumeration and system hacking. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 Linux system has a script named 'backup' owned by root with the SUID bit set and world-executable permissions. A standard user executes the script and discovers it runs a command that reads /etc/shadow and writes output to a world-readable file. What is the most likely intended exploitation path?
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
✓
SUID abuse to read sensitive files
Option C is correct because the SUID bit on the 'backup' script, owned by root and world-executable, allows any user to execute it with root privileges. If the script reads /etc/shadow (which is normally root-only) and writes the output to a world-readable file, an attacker can exploit this to exfiltrate password hashes. This is a classic SUID abuse scenario where a privileged binary or script is used to access sensitive files.
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.
✗
GUID abuse
Why it's wrong here
GUID (group ID) would grant group privileges, not root. The SUID bit is set for the owner (root).
✗
LD_PRELOAD injection
Why it's wrong here
LD_PRELOAD could be used to hijack libraries, but the direct attack here is via SUID.
✓
SUID abuse to read sensitive files
Why this is correct
The SUID bit makes the script run as root, so it can read /etc/shadow. Users can exploit this to get hashes.
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.
✗
Token impersonation
Why it's wrong here
Token impersonation is a Windows technique, not Linux.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse SUID with SGID or think LD_PRELOAD works on scripts, but the key is recognizing that SUID on a root-owned executable enables privilege escalation to read /etc/shadow, while LD_PRELOAD only applies to dynamically linked binaries, not scripts.
Detailed technical explanation
How to think about this question
Under the hood, the SUID bit (chmod u+s) sets the effective UID to the file owner (root) during execution, overriding the real UID of the calling user. Even if the script is a shell script, many Linux distributions ignore SUID on interpreted scripts for security reasons (due to race conditions and shell invocation), but if the system allows it or the script is a compiled binary, the exploit works. In real-world scenarios, attackers often scan for SUID binaries like 'find' or 'nmap' that can spawn shells or read files, and a custom 'backup' script is a prime target for privilege escalation.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Enumeration and System Hacking — This question tests Enumeration and System Hacking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: SUID abuse to read sensitive files — Option C is correct because the SUID bit on the 'backup' script, owned by root and world-executable, allows any user to execute it with root privileges. If the script reads /etc/shadow (which is normally root-only) and writes the output to a world-readable file, an attacker can exploit this to exfiltrate password hashes. This is a classic SUID abuse scenario where a privileged binary or script is used to access sensitive files.
What should I do if I get this CEH 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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