Access Control Implementation
Using ACLs and permissions to restrict access to resources based on user identity, role, or attributes. Implementing the principle of least privilege to minimize exposure.
Understanding Access Control Implementation
Access control implementation restricts who can access resources and what actions they can perform. Properly implemented access controls prevent unauthorized access, limit damage from compromised accounts, and support compliance requirements.
Key access control principles: • Least privilege — Minimum access needed for job function • Need to know — Access only to required information • Separation of duties — No single person controls entire process • Defense in depth — Multiple layers of access control
Access control is a fundamental mitigation technique that limits both external attackers and insider threats.
Why This Matters for the Exam
Access control implementation is heavily tested on SY0-701 as it applies across all security domains. Questions cover ACL configuration, permission models, and the principle of least privilege.
Understanding access control helps with security design, policy creation, and incident response. Overly permissive access is a root cause of many breaches.
The exam tests both conceptual models (DAC, MAC, RBAC) and practical implementation (file permissions, network ACLs).
Deep Dive
Access Control Lists (ACLs)
Lists specifying which subjects can access objects and what operations they can perform.
Network ACLs:
- •Filter traffic by source/destination IP
- •Control port/protocol access
- •Applied to router interfaces
- •Permit or deny rules processed in order
Network ACL Example:
- •```
- •permit tcp 10.1.1.0/24 any eq 443 # Allow HTTPS out
- •permit tcp 10.1.1.0/24 any eq 80 # Allow HTTP out
- •deny ip 10.1.1.0/24 10.2.0.0/16 # Block server network
- •permit ip any any # Allow rest
- •```
File System ACLs:
- •Define user/group permissions on files
- •Read, write, execute permissions
- •Inheritance from parent folders
- •Windows NTFS and Linux extended ACLs
Windows NTFS Permissions:
| Permission | Allows |
|---|---|
| Full Control | All actions including changing permissions |
| Modify | Read, write, delete, execute |
| Read & Execute | View and run files |
| Read | View contents only |
| Write | Create and modify |
Principle of Least Privilege
Granting minimum access required to perform job functions.
Least Privilege Implementation:
- •Default deny all access
- •Grant specific permissions as needed
- •Regular access reviews
- •Remove access when no longer needed
- •Time-limited elevated access
Least Privilege Examples:
| Role | Appropriate Access |
|---|---|
| Help Desk | Password reset, not full admin |
| Developer | Dev servers, not production |
| Accountant | Finance systems, not HR data |
| Auditor | Read access, not write |
Benefits:
- •Limits damage from compromises
- •Reduces insider threat risk
- •Simplifies auditing
- •Supports compliance
Role-Based Access Control (RBAC)
Assigning permissions to roles, then users to roles.
RBAC Structure:
- •```
- •Roles define permissions:
- •├── Admin Role → Full system access
- •├── Manager Role → Read/write department data
- •├── User Role → Read own data, limited write
- •└── Guest Role → Read public data only
Users assigned to roles: ├── jsmith → Manager Role ├── bjones → User Role └── mwilson → Admin Role ```
RBAC Benefits:
- •Easier administration (manage roles, not individuals)
- •Consistent access across similar users
- •Easier auditing
- •Scalable for large organizations
RBAC vs. Other Models:
| Model | Description | Control |
|---|---|---|
| DAC | Owner controls access | Discretionary |
| MAC | Labels/classifications | Mandatory |
| RBAC | Roles determine access | Role-based |
| ABAC | Attributes determine access | Attribute-based |
Attribute-Based Access Control (ABAC)
Access decisions based on attributes of user, resource, and environment.
ABAC Attributes:
- •User: Role, department, clearance, location
- •Resource: Classification, owner, type
- •Environment: Time, location, device
- •Action: Read, write, delete
ABAC Example:
- •```
- •IF user.department = "Finance"
- •AND resource.type = "Financial Report"
- •AND time.hours BETWEEN 9 AND 17
- •AND user.location = "Corporate Network"
- •THEN permit.read
- •```
Permission Implementation
File Permissions Best Practices:
- •Apply to groups, not individuals
- •Use inheritance appropriately
- •Regular permission audits
- •Document permission decisions
- •Remove excessive permissions
Linux Permissions:
- •```
- •rwxr-xr-- (754)
- •├── Owner: read, write, execute
- •├── Group: read, execute
- •└── Other: read only
- •```
Access Review Process:
- 1.Identify all user access
- 2.Verify access is still required
- 3.Remove unnecessary permissions
- 4.Document exceptions
- 5.Schedule regular reviews (quarterly)
How CompTIA Tests This
Example Analysis
Scenario: A junior developer is granted local administrator access to their workstation for convenience. They accidentally install malware while browsing, which uses the admin privileges to disable antivirus, install a keylogger, and spread to network shares the developer has write access to.
Analysis - Least Privilege Violation:
What Went Wrong: • Developer had admin rights (unnecessary for job) • Malware inherited admin privileges • Could disable security controls • Had excessive network share access
Proper Implementation:
Workstation Access: • Standard user for daily tasks • Admin access only through separate account • Admin access requires approval and justification • Time-limited elevation when needed
Network Access: • Read-only to shared resources by default • Write access only to project folders • No access to production systems • Access reviewed quarterly
How Least Privilege Would Help: 1. Developer runs as standard user 2. Malware executes with standard privileges 3. Cannot disable antivirus (requires admin) 4. Cannot modify system files 5. Limited to user's data, not network-wide spread
Key insight: Every unnecessary permission is potential attack surface. Least privilege limits what attackers (or malware) can do with compromised accounts.
Key Terms to Know
Common Mistakes to Avoid
Exam Tips
Memory Trick
"LPNK" - Access Control Principles
- •Least privilege (minimum access)
- •Permission reviews (regular audits)
- •Need to know (access to required info only)
- •Keep separated (separation of duties)
- •Access Control Models: "DRAM"
- •DAC = Discretionary (owner decides)
- •RBAC = Role-based (roles have permissions)
- •ABAC = Attribute-based (dynamic decisions)
- •MAC = Mandatory (labels/classifications)
Least Privilege Visual: "Give a KEY only to the rooms they NEED" Not master key to entire building
ACL Rule Order: "First match wins" More specific rules before general rules End with implicit deny
Permission Assignment: Users → Roles → Permissions (Not: Users → Permissions directly)
Test Your Knowledge
Q1.A user needs temporary access to a sensitive system for a one-week project. According to least privilege principles, what is the best approach?
Q2.An organization manages access by assigning users to groups like "Finance-Read" and "Finance-Write" rather than granting permissions to individual users. This is an example of:
Q3.What is the PRIMARY purpose of implementing the principle of least privilege?
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