Linux Security

Linux security encompasses the principles, tools, and configurations used to safeguard systems running the Linux operating system from unauthorized access, modification, or disruption. This multi-layered approach is fundamentally built on a robust permission model for users and groups, which governs access to files and resources. For more stringent control, it utilizes Mandatory Access Control (MAC) frameworks like SELinux or AppArmor to enforce system-wide security policies that constrain the actions of all processes, including those running with root privileges. The practice also extends to network security through firewalls, system monitoring via auditing and logging, and kernel hardening to minimize the attack surface and create a resilient computing environment.

1. Introduction to Linux Security
   1. Core Security Principles
      1. Confidentiality
         1. Data Privacy Concepts
         2. Information Classification
         3. Access Restrictions
         4. Data Leakage Prevention
      2. Integrity
         1. Data Consistency
         2. Change Detection
         3. Hash Verification
         4. Digital Signatures
      3. Availability
         1. System Uptime Requirements
         2. Service Reliability
         3. Denial of Service Prevention
         4. Redundancy and Failover
      4. Authentication
         1. Identity Verification
         2. Multi-factor Authentication
         3. Single Sign-On Concepts
      5. Authorization
         1. Permission Models
         2. Access Decision Making
         3. Privilege Escalation Prevention
      6. Accountability
         1. Audit Trails
         2. Non-repudiation
         3. Activity Tracking
   2. The Linux Security Model
      1. Discretionary Access Control (DAC)
         1. User and Group Ownership
         2. Permission Bits
         3. Access Control Inheritance
      2. Mandatory Access Control (MAC)
         1. Policy Enforcement
         2. Security Labels
         3. Classification Levels
         4. Information Flow Control
      3. Role-Based Access Control (RBAC)
         1. Role Definition
         2. Role Assignment
         3. Role Permissions
         4. Role Hierarchies
      4. Attribute-Based Access Control (ABAC)
         1. Policy Rules
         2. Attribute Evaluation
         3. Dynamic Access Decisions
   3. Understanding Attack Surfaces and Vectors
      1. Local Attack Vectors
         1. Privilege Escalation
         2. Buffer Overflows
         3. Race Conditions
         4. Symlink Attacks
      2. Remote Attack Vectors
         1. Network Service Exploits
         2. Protocol Vulnerabilities
         3. Man-in-the-Middle Attacks
      3. Social Engineering Risks
         1. Phishing Attacks
         2. Pretexting
         3. Physical Security Breaches
      4. Software Vulnerabilities
         1. Code Injection
         2. Memory Corruption
         3. Logic Flaws
         4. Supply Chain Attacks
   4. Security Design Principles
      1. Principle of Least Privilege
         1. Minimizing User Privileges
         2. Limiting Process Capabilities
         3. Reducing Attack Surface
      2. Defense in Depth
         1. Layered Security Controls
         2. Redundant Protection Mechanisms
      3. Fail-Safe Defaults
         1. Secure Default Configurations
         2. Error Handling Security
      4. Complete Mediation
         1. Access Control Enforcement
         2. Bypass Prevention
      5. Open Design
         1. Security Through Transparency
         2. Avoiding Security by Obscurity
   5. Linux Security Architecture
      1. Kernel Security Features
         1. Memory Protection
         2. Process Isolation
         3. System Call Interface
      2. User Space Security
         1. Application Sandboxing
         2. Library Security
         3. Runtime Protection