Lecture 2: Network Security Physical Layer

목차

Network Security

Network security is the protection of the underlying networking infrastructure from unauthorized access, misuse, or theft.

It involves creating a secure infrastructure for devices, users, and applications to wokr in a secure manner.

 

 

A Network

A network consists of two or more computers that are linked to share resources, exchange files, or allow electronic communications.

The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.

 

 

The OSI Model

The OSI (Open Systems Interconnection) Model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven abstract layers.

In practice we only use five layers and security is imporant for every single layer.

 

e.g. Traffic on your device

 

 

 

The physical layer

Physical security is the first line of defense against unauthorized access, environmental hazards, and theft.

Without adequate physical security, even the most robust cybersecurity measures can be compromised.

 

Ex) Physical layer threat examples

 

 

Cables can be tapped or cut. (케이블이 도청되거나 잘렸을 때)

CIA Triad에서 Confidentiality, 즉 기밀성이 성립되지 않을 수가 있다. 

→ Unauthorized individuals may gain access to sensitive data by intercepting the communication

 

 

Physical Layer Threats

Wiretaps, fiber taps (도청)

 

Detecting taps

- Physical inspection (직접 점검)

- Signal strength analysis

- Cable testing (using time-domain reflectometer)

 

 

More cable threats

Electromagnetic Interference (EMI) (전자파 장애): 

Electrical devices, power cables, and other equipment emitting electromagnetic interference can negatively impact the performance of network cables.

Proper cable shielding and separation from other electronic devices can minimize EMI.

 

Rodent or Pest Damage (설치류로 인한 손상):

Rodents or pests may chew through cables, causing disruptions to network connectivity.

Proper cable management and protective coverings can help prevent such damage.

 

 

Physical Layer Threats - Submarine cables (해저 케이블)

 

의도적으로 해저 케이블을 잘랐을 때 통신 오류 발생 가능.

 

 

Guided vs Unguided Media

A guided medium is a communication channel where the signals are guided along a physical path (physical cables)

- Physical access is needed to tamper with the data on the cable (케이블을 직접 접근해야 데이터를 손댈 수 있음)

유도 매체: 선이 있는 매체

 

 

An unguided medium refers to a communication channel where the signals propagate freely through the air or space. 

e.g. Radio waves, infrared waves

비유도 매체: 물리적 도체 없이 신호를 전달하는 매체 (Wireless)

e.g. Bluetooth, WiFi, satellite communications, GPS (Global Positioning System)

Access control on unguided media is hard → they propagate in all directions and can be intercepted over a wide area, making it difficult to physically control access to the transmission medium.

 

 

Signal Security

Spread signals over multiple frequencies to counter jamming.

Frequency hopping aims to change frequencies very fast in a pattern that is unknown to an attacker.

Frequency hopping = 주파수 도약. 반송파의 주파수가 고정되어 있지 않고, 다양한 주파수로 바뀌며 도약하는 통신방식. 이렇게 하면 도청당할 확률/위험성이 비교적 적음.

Authenticating and encrypting data sent over wireless signals can ensure integrity and confidentiality.

아니면 데이터를 암호화해서 비유도 매체로 보내면 무결성과 기밀성 확보.