This CKS practice question tests your understanding of system hardening. 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.
An attacker exploited a container escape vulnerability. The team wants to mitigate such attacks by restricting containers from accessing the host's kernel capabilities. Which set of capabilities should be dropped from all containers?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
SYS_ADMIN, SYS_MODULE, SYS_PTRACE
Option A is correct because SYS_ADMIN, SYS_MODULE, and SYS_PTRACE are the most dangerous capabilities that enable container escape. SYS_ADMIN grants broad administrative privileges (e.g., mounting filesystems, accessing /proc/1/environ), SYS_MODULE allows loading kernel modules, and SYS_PTRACE permits tracing processes outside the container. Dropping these three capabilities is a key mitigation against kernel-level escapes.
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.
✓
SYS_ADMIN, SYS_MODULE, SYS_PTRACE
Why this is correct
These capabilities allow kernel module loading, system administration, and process tracing, which can be exploited for escape.
Related concept
Read the scenario before looking for a memorised answer.
✗
CHOWN, DAC_OVERRIDE, FOWNER
Why it's wrong here
These allow file permission changes but are less likely to cause escape.
✗
KILL, SETPCAP, SYS_CHROOT
Why it's wrong here
SYS_CHROOT can be dangerous, but KILL and SETPCAP are less critical.
✗
NET_RAW, NET_ADMIN, NET_BIND_SERVICE
Why it's wrong here
These are network capabilities, not typically used for container escape.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the misconception that all capabilities are equally dangerous, but the trap here is that candidates may choose networking or file capabilities (options B, C, D) because they sound security-relevant, while the actual escape vector relies on the three kernel-focused capabilities in option A.
Detailed technical explanation
How to think about this question
Under the hood, SYS_ADMIN (cap_sys_admin) allows mounting cgroup hierarchies and accessing /proc/self/root, which can be exploited to escape via cgroup release_agent or pivot_root attacks. SYS_MODULE (cap_sys_module) enables inserting kernel modules via `insmod`, giving an attacker full kernel control. SYS_PTRACE (cap_sys_ptrace) allows attaching to host processes via ptrace, enabling memory reads and code injection. In practice, dropping these three capabilities is recommended by the CIS Benchmark for Docker and the NSA Kubernetes Hardening Guide.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
System Hardening — This question tests System Hardening — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: SYS_ADMIN, SYS_MODULE, SYS_PTRACE — Option A is correct because SYS_ADMIN, SYS_MODULE, and SYS_PTRACE are the most dangerous capabilities that enable container escape. SYS_ADMIN grants broad administrative privileges (e.g., mounting filesystems, accessing /proc/1/environ), SYS_MODULE allows loading kernel modules, and SYS_PTRACE permits tracing processes outside the container. Dropping these three capabilities is a key mitigation against kernel-level escapes.
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.
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Question Discussion
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