Quick Answer
The answer is access control lists (ACLs) on files, as they provide the most granular access control over user permissions in a defense-in-depth strategy. ACLs achieve this by allowing permissions to be set at the individual file or object level, specifying exactly which users or groups can read, write, execute, or modify that specific resource—far more precise than broader mechanisms like network segmentation or firewall rules, which operate at the subnet level. On the ISC2 Certified in Cybersecurity CC exam, this question tests your understanding of how ACLs implement discretionary access control (DAC) within file systems such as NTFS or ext4, and a common trap is confusing network-level controls with object-level permissions. Remember the memory tip: “ACLs go granular, firewalls go general”—if you need to control a single file, think ACLs, not a network rule.
This CC practice question tests your understanding of access controls concepts. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
In a defense-in-depth strategy, which access control mechanism provides the most granular control over user permissions?
Network segmentation
Why wrong: Segmentation isolates network traffic but does not control user permissions on files.
Access control lists (ACLs) on files
ACLs provide fine-grained control over who can read, write, or execute individual files.
Physical security controls
Why wrong: Physical controls limit physical access, not digital permissions.
Firewall rules
Why wrong: Firewall rules control network access, not user-level file permissions.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Access control lists (ACLs) on files
Access control lists (ACLs) on files provide the most granular control because they allow permissions to be set at the individual file or object level, specifying exactly which users or groups can read, write, execute, or modify that specific resource. This is in contrast to broader mechanisms like network segmentation or firewall rules, which operate at the network or subnet level and cannot distinguish between individual files within a system. ACLs are a fundamental component of discretionary access control (DAC) and are implemented in file systems such as NTFS, ext4, and ZFS.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Network segmentation
Why it's wrong here
Segmentation isolates network traffic but does not control user permissions on files.
Access control lists (ACLs) on files
Why this is correct
ACLs provide fine-grained control over who can read, write, or execute individual files.
Related concept
Read the scenario before looking for a memorised answer.
Physical security controls
Why it's wrong here
Physical controls limit physical access, not digital permissions.
Firewall rules
Why it's wrong here
Firewall rules control network access, not user-level file permissions.
Common exam traps
ISC2 often tests the distinction between network-level controls (like firewall rules and segmentation) and system-level controls (like file ACLs), leading candidates to mistakenly choose a network mechanism when the question asks for the most granular control over user permissions on a resource.
Detailed technical explanation
File ACLs are stored as part of the file's metadata in the file system, often using a security descriptor that contains a discretionary access control list (DACL) and a system access control list (SACL). In Windows NTFS, each ACL entry (ACE) specifies a security identifier (SID) and a set of access rights (e.g., FILE_READ_DATA, FILE_WRITE_DATA), allowing up to 14 distinct permissions. In a real-world scenario, an ACL can deny a specific user write access to a sensitive document while granting full control to an administrator, a level of precision that network segmentation or firewall rules cannot achieve.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
What to study next
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FAQ
Access Controls Concepts — This question tests Access Controls Concepts — Read the scenario before looking for a memorised answer..
The correct answer is: Access control lists (ACLs) on files — Access control lists (ACLs) on files provide the most granular control because they allow permissions to be set at the individual file or object level, specifying exactly which users or groups can read, write, execute, or modify that specific resource. This is in contrast to broader mechanisms like network segmentation or firewall rules, which operate at the network or subnet level and cannot distinguish between individual files within a system. ACLs are a fundamental component of discretionary access control (DAC) and are implemented in file systems such as NTFS, ext4, and ZFS.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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