Operating System (OS) security is a critical aspect of cybersecurity, focusing on protecting the OS from threats and ensuring the integrity, confidentiality, and availability of the data it manages. This module will cover the fundamental concepts, techniques, and tools used to secure operating systems.

• Discretionary Access Control (DAC): Access control based on the identity of the requestor and access rules stating what requestors are (or are not) allowed to do.
• Mandatory Access Control (MAC): Access control based on comparing security labels with security clearances.
• Role-Based Access Control (RBAC): Access control based on the roles assigned to users within an organization.

• Authentication: Verifying the identity of a user, process, or device.
  • Methods: Passwords, biometrics, multi-factor authentication (MFA).
• Authorization: Determining what an authenticated user is allowed to do.
  • Methods: Access control lists (ACLs), capability lists.

• Patch Management: The process of managing updates for software applications and technologies.
  • Importance: Fixes security vulnerabilities, improves functionality, and ensures compliance.

• User Account Control (UAC): Limits application software to standard user privileges until an administrator authorizes an increase in privilege level.
• Data Execution Prevention (DEP): Prevents code from being executed from data pages such as the default heap, stacks, and memory pools.
• Address Space Layout Randomization (ASLR): Randomizes the memory addresses used by system and application processes to prevent buffer overflow attacks.

Explanation:

• adduser newuser: Creates a new user account named newuser.
• passwd newuser: Sets a password for the newuser account.

Explanation:

• ufw allow ssh: Allows incoming SSH connections.
• ufw default deny incoming: Denies all incoming connections by default.
• ufw default allow outgoing: Allows all outgoing connections by default.
• ufw enable: Enables the firewall with the specified rules.

1. Create a new user named testuser.
2. Set a password for testuser.
3. Add testuser to the sudo group.

Solution:

1. Allow HTTP and HTTPS traffic.
2. Deny all other incoming connections.
3. Enable the firewall.

Solution:

• Common Mistake: Forgetting to update the OS and software regularly.
  • Tip: Implement an automated patch management system to ensure timely updates.
• Common Mistake: Using weak passwords for user accounts.
  • Tip: Enforce strong password policies and consider using MFA.
• Common Mistake: Misconfiguring firewall rules.
  • Tip: Regularly review and test firewall rules to ensure they are correctly configured.

In this section, we covered the essential aspects of operating system security, including security models, user authentication and authorization, patch management, and security features in modern operating systems. By understanding and implementing these concepts, you can significantly enhance the security posture of your operating systems. Next, we will delve into web application security, exploring the unique challenges and solutions in that domain.