Question 374 of 997

Monitoring, Logging and Runtime Security →hardMultiple ChoiceObjective-mapped

Writing a Falco Rule to Detect Container Reads of /etc/shadow

This CKS practice question tests your understanding of monitoring, logging and runtime security. 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.

You are writing a Falco rule to detect when a container tries to read the file `/etc/shadow`. Which condition in the Falco rule correctly matches this event?

A
container.name=shadow and evt.type=open
Why wrong: container.name is the container name, not the file path.
B
evt.type=read and fd.name=/etc/shadow
Why wrong: The read syscall often does not have fd.name populated; open is the correct syscall to capture file access.
C
proc.name=cat and fd.name=/etc/shadow
Why wrong: This only detects if the process name is 'cat', which is too specific and misses other tools.
D
evt.type=open and fd.name=/etc/shadow
The open syscall is used to open files, and fd.name contains the file path. This correctly detects attempts to open /etc/shadow.

Full breakdown with real-world context →

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

✓

evt.type=open and fd.name=/etc/shadow

Option D is correct because Falco rules use conditions that match system calls (evt.type) and file descriptors (fd.name). The event type 'open' is the syscall used to open a file for reading, and fd.name='/etc/shadow' specifies the target file. This combination correctly detects when a container attempts to open /etc/shadow, which is the typical first step before reading it.

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.

✗
container.name=shadow and evt.type=open
Why it's wrong here
container.name is the container name, not the file path.
✗
evt.type=read and fd.name=/etc/shadow
Why it's wrong here
The read syscall often does not have fd.name populated; open is the correct syscall to capture file access.
✗
proc.name=cat and fd.name=/etc/shadow
Why it's wrong here
This only detects if the process name is 'cat', which is too specific and misses other tools.
✓
evt.type=open and fd.name=/etc/shadow
Why this is correct
The open syscall is used to open files, and fd.name contains the file path. This correctly detects attempts to open /etc/shadow.
Related concept
Read the scenario before looking for a memorised answer.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The CKS exam often tests the misconception that 'evt.type=read' is the correct syscall for detecting file reads, but the trap is that 'read' operates on an already-opened file descriptor, while 'open' is the syscall that reveals the file path being accessed.

Detailed technical explanation

How to think about this question

Falco monitors system calls via kernel modules or eBPF, and the 'open' syscall (or 'openat') is the entry point for file access. The condition 'evt.type=open and fd.name=/etc/shadow' triggers on the open event, which occurs before any read, making it a reliable detection point. In real-world scenarios, attackers might use tools like 'dd', 'head', or custom binaries to read /etc/shadow, so relying on 'proc.name' would miss those cases.

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 practitioner preparing for the CKS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.

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.

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FAQ

Questions learners often ask

What does this CKS question test?

Monitoring, Logging and Runtime Security — This question tests Monitoring, Logging and Runtime Security — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: evt.type=open and fd.name=/etc/shadow — Option D is correct because Falco rules use conditions that match system calls (evt.type) and file descriptors (fd.name). The event type 'open' is the syscall used to open a file for reading, and fd.name='/etc/shadow' specifies the target file. This combination correctly detects when a container attempts to open /etc/shadow, which is the typical first step before reading it.

What should I do if I get this CKS question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

About these practice questions

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Same concept, more angles

1 more ways this is tested on CKS

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. You are writing a Falco rule to detect when a container tries to read /etc/shadow. Which condition should you use?

medium

✓ A.fd.name=/etc/shadow and container.id != host
B.fd.name=/etc/passwd
C.container.id != host
D.fd.name=/etc/shadow

Why A: The correct condition 'fd.name=/etc/shadow and container.id != host' ensures the accessed file is /etc/shadow and the event originates from a container (not the host). Option A correctly includes both conditions. Option B specifies /etc/passwd (wrong file). Option C only checks that it's from a container but does not restrict the file. Option D checks the file but does not exclude host events.

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