What Is Operating System Security? — 10 Minutes of Operating Systems, Day 16

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Before We Begin 🔗

Operating system security goes beyond blocking viruses. It includes preventing intrusions and malicious code execution,

keeping files safe, and preventing users from interfering with one another

We will look at

security concepts, types of threats, authentication and encryption, and real-world defenses

through examples simple enough for a child to follow.

What Is Operating System Security? 🔗

Operating system security is the set of techniques that

protect system resources and user data from unauthorized access and malicious activity

Imagine lockers at school. Each locker has a lock that keeps other students from opening it. The lock is like a security mechanism such as encryption or user authentication.

Some lockers may use a password, while others open only when you scan your fingerprint. Those are examples of password and biometric authentication. If the contents themselves can only be read with a particular code, that's like encrypted information.

The operating system needs to protect resources and information such as these:

Memory, the CPU, files, and network resources
User data and preferences
System settings and the kernel

Types of System Threats 🔗

Operating systems have to defend against a variety of threats. Here are some common ones.

1. Program-Based Threats 🔗

Virus
— malicious code that hides in executable files and spreads.
Worm
— a program that spreads on its own across a network.
Trojan horse
— a program that looks legitimate but behaves maliciously.

예: 어떤 사진 뷰어 프로그램을 실행했는데, 백그라운드에서 내 파일을 외부로 전송한다면? 트로이 목마일 수 있습니다.

2. System and Network Threats 🔗

Sniffing
— secretly observing data traveling over a network.
Spoofing
— impersonating another user or server.
Denial of service (DoS)
— overwhelming resources so a system cannot function normally.

Authentication and Encryption 🔗

Operating systems use

authentication and encryption

together to keep information safe.

User Authentication 🔗

Authentication verifies a user's identity.

Password-based authentication
— a user ID and password.
Two-factor authentication
— a code sent by text, email verification, or a similar second step.
Biometric authentication
— a fingerprint, facial recognition, or another biometric.

예: 스마트폰에서 비밀번호 입력 + 지문 인식 → 이중 인증 적용

What Is Encryption? 🔗

Encryption

transforms information so other people cannot understand it

Imagine writing a secret letter to a friend and replacing ‘ABC’ with ‘123’ before sending it.

Symmetric encryption
uses the same secret key to lock and unlock information. If someone else learns the key, the protection is lost. It's like sharing a house key with a friend.
Asymmetric encryption
uses two keys. The public key can be shared, while the private key is kept secret. Information locked with the public key can only be opened with the private key, which helps protect it. It's like a friend sending you a padlock while keeping the only key.

Security Defenses and Operating System Examples 🔗

Operating systems use several defenses internally.

Common Defenses 🔗

Firewall
— monitors incoming connections and lets only permitted traffic through, like a school gate that admits only people with a pass.
Separation of user privileges
— giving every user full control would be risky. The operating system distinguishes ordinary users from administrators (superusers), allowing only administrators to make important system changes.
Access control list (ACL)
— specifies who can read, write, or execute each file or folder. It's like using a house key to enforce a rule that only Mom can enter a particular room.
Logging and auditing
— record who opened or modified a file and when. Like security camera footage, these records help trace what happened when something goes wrong.

App-Level Security Matters Too 🔗

On modern smartphones and tablets,

the security of individual apps

matters alongside operating system security.

Each app runs in a
sandbox
that keeps it from reading other apps' data.
App permissions
can restrict access to location, the camera, and the microphone.

예: 사진 편집 앱이 위치 정보에 접근하려고 하면, 허용할지 묻는 창이 뜨는 이유입니다.

Example: Security in Windows 10 🔗

Windows Defender
— built-in antivirus.
SmartScreen
— blocks suspicious apps from running.
BitLocker
— encrypts the entire disk to prevent data exposure.

Summary 🔗

Operating system security is a major line of defense for computers and their data. We looked at how it works across several layers, including programs, networks, user authentication, and app permissions.

Next time, we will cover

access control and permission management

, two core parts of operating system protection.

References 🔗

Operating System Concepts (10th Edition)
https://en.wikipedia.org/wiki/Computer_security↗
https://learn.microsoft.com/en-us/windows/security↗

What Is Operating System Security? — 10 Minutes of Operating Systems, Day 16 | PromleeBlog