The answer is the combination of SUID privilege escalation and an LD_PRELOAD rootkit. The attacker set the SUID bit on a non-standard binary owned by root, allowing any user to execute it with root privileges, while the LD_PRELOAD rootkit—loaded via /etc/ld.so.preload—hooks system calls to hide malicious processes and files, explaining the log gaps during peak hours. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of Linux persistence and evasion techniques, often appearing as a multi-step attack where SUID provides initial elevation and LD_PRELOAD maintains stealth. A common trap is confusing LD_PRELOAD with simple library injection; remember that /etc/ld.so.preload is a global, persistent rootkit mechanism that loads before all other libraries. Memory tip: “SUID lifts you up, LD_PRELOAD hides your tracks.”
CEH Enumeration and System Hacking Practice Question
This CEH practice question tests your understanding of enumeration and system hacking. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 security analyst is investigating a compromised Linux system and finds the following: - A binary with SUID bit set owned by root that is not a standard system binary - The file /etc/ld.so.preload contains a reference to a shared object in /tmp - The system logs show gaps of several minutes during peak hours. Which TWO techniques has the attacker MOST likely used to maintain access and evade detection?
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 privilege escalation
Options A and B are correct. SUID abuse allows executing a binary with root privileges. LD_PRELOAD via ld.so.preload can be used to hook system calls and hide files/processes (a rootkit technique). Log manipulation (gaps) is another covering tracks method.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
SUID privilege escalation
Why this is correct
Setting SUID on a root-owned binary allows any user to run it with root privileges.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
Password cracking
Why it's wrong here
No evidence of password cracking; the focus is on persistence and evasion.
✗
Kernel module rootkit
Why it's wrong here
Kernel module rootkits typically load a .ko file, not via ld.so.preload.
✓
LD_PRELOAD rootkit
Why this is correct
Loading a shared object via /etc/ld.so.preload can intercept system calls to hide malicious activity.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
Steganography
Why it's wrong here
No indication of hidden data within files.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CEH questions on access control and AAA configuration.
Enumeration and System Hacking — This question tests Enumeration and System Hacking — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: SUID privilege escalation — Options A and B are correct. SUID abuse allows executing a binary with root privileges. LD_PRELOAD via ld.so.preload can be used to hook system calls and hide files/processes (a rootkit technique). Log manipulation (gaps) is another covering tracks method.
What should I do if I get this CEH question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CEH questions on access control and AAA configuration.
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?
Authentication checks who the user is.
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