CS2005 – Networks and Operating Systems: Security

Vocabulary flashcards covering security threats, attacks, protection levels, malware, and fundamental cryptography concepts from the lecture notes.

Security

A system state in which resources are used and accessed exactly as intended under all circumstances.

Attack

An active attempt to breach or compromise system security.

Threat

A potential security violation that could cause damage if realized.

Intruder

A person who tries to gain unauthorised access to a system, violate security, or damage data.

Breach of Confidentiality

Unauthorised access to or theft of information (e.g., credit-card data).

Breach of Integrity

Unauthorised modification of data (e.g., defacing a website).

Breach of Availability

Unauthorised destruction or disruption of data or services.

Theft of Service

Unauthorised use of resources, such as installing a hidden file server daemon.

Denial of Service (DoS)

Preventing legitimate use of a system by overwhelming it with illegitimate traffic.

Masquerading

An attacker pretends to be another host or user to gain privileges.

Replay Attack

Malicious or fraudulent repeat of a valid data transmission, often involving message modification.

Man-in-the-Middle Attack

Attacker inserts into a communication flow, impersonating each side to the other.

Session Hijacking

Intercepting an active session to bypass authentication and assume the connection.

Physical Security

Protecting data centres, servers, and terminals against physical tampering or theft.

Human Security

Reducing risks from social engineering, phishing, dumpster diving, etc.

Operating-System Security

OS protection mechanisms (e.g., permissions, debugging controls) that enforce access limits.

Network Security

Safeguards against intercepted communications, interruptions, and network-based DoS attacks.

Trojan Horse

A program that disguises itself as legitimate, may block/alter data or install a backdoor, but cannot self-replicate.

Trap Door (Backdoor)

Hidden mechanism (e.g., hard-coded credentials) left in software to bypass normal authentication.

Logic Bomb

Malicious code triggered by specific conditions such as a date or event.

Stack/Buffer Overflow

Attack technique that overwrites return addresses on the stack to hijack program control.

Virus

Self-replicating code fragment embedded in legitimate programs, capable of spreading to other machines.

File (Parasitic) Virus

Virus type that attaches to executable files.

Boot/Memory Virus

Infects boot sectors or memory to gain control during system start-up.

Macro Virus

Written in application macro languages (e.g., VB) and infects documents or templates.

Source-Code Virus

Inserts itself into source files so it later propagates when the code is compiled.

Polymorphic Virus

Changes form to avoid detection by signature-based scanners.

Worm

Standalone, self-replicating program that spawns copies across a network, consuming resources.

Port Scanning

Automated attempt to connect to multiple ports/IPs to discover exploitable services.

Morris Internet Worm

1988 worm by Robert T. Morris that exploited UNIX vulnerabilities; one of the first Internet worms.

Cryptography

The science of secret writing; techniques for secure communication via codes and ciphers.

Encryption

Process of encoding plaintext into ciphertext using an algorithm and key.

Decryption

Reversing encryption to obtain plaintext from ciphertext using the appropriate key.

Cipher

Algorithm that performs encryption and decryption operations.

Plaintext

The original, unencrypted message.

Ciphertext

The encrypted form of a message.

Cryptosystem

A set of algorithms for encryption, decryption, and key generation.

Cryptanalysis

The study of methods to break or circumvent encryption schemes.

Symmetric Encryption

Encryption where the same secret key is used for both encryption and decryption.

Block Cipher

Symmetric cipher that processes fixed-size blocks of data (e.g., DES, AES).

Stream Cipher

Symmetric cipher that encrypts data as a continuous stream (e.g., RC4).

DES (Data Encryption Standard)

Early NIST-adopted block cipher; now considered insecure for many uses.

Triple DES

An enhanced DES version applying the cipher three times for stronger security.

AES (Advanced Encryption Standard)

Modern NIST-standard block cipher replacing DES for most applications.

RC4

Stream cipher by Ron Rivest (1987); considered insecure today.

Key Exchange

Process of sharing a secret key directly or via a trusted third party (certificate authority).

Asymmetric Encryption (Public-Key)

Encryption using different keys: a public key for encryption and a private key for decryption.

Public Key

Non-secret key distributed openly to allow others to encrypt messages for the key owner.

Private Key

Secret key held by the owner to decrypt messages encrypted with the corresponding public key.

RSA Algorithm

Widely used public-key algorithm relying on the difficulty of factoring large composite numbers.