Fundamentals of Computer Security

Introduction to Computer Security

Computer Security is defined as the prevention and detection of unauthorized actions by users of a computer system. It encompasses all measures designed to protect computer systems, networks, and data from unauthorized access, modification, destruction, or disclosure.

Security is not just a technical issue—it requires a combination of technology, policies, procedures, and most importantly, security-conscious personnel. Even the most sophisticated technical controls can be circumvented by careless users.

The CIA Triad

The CIA Triad forms the foundation of computer security and consists of three core principles that must be protected:

1. Confidentiality

Confidentiality prevents unauthorized disclosure of information, keeping data secret or private. This applies to military secrets, business documents, personal information, and any data that should not be shared with unauthorized parties.

• Data Classification: Information is categorized by sensitivity level (public, internal, confidential, secret)
• Access Controls: Only authorized individuals can access specific information
• Encryption: Data is transformed to prevent understanding by unauthorized parties
• Examples: Personal health records, financial statements, trade secrets, passwords

2. Integrity

Integrity prevents unauthorized writing or modification of information, ensuring data accuracy and consistency. It means that information remains complete and unaltered throughout its lifecycle.

• Data Accuracy: Information is correct and has not been tampered with
• Consistency: Data across systems matches and is coherent
• Non-repudiation: Entities cannot deny their actions
• Examples: Financial transactions, medical records, legal documents

3. Availability

Availability ensures that information is accessible and usable upon appropriate demand by authorized users. Systems must be operational when needed to support business operations.

• Uptime: Systems are operational when needed
• Performance: Systems respond quickly to legitimate requests
• Redundancy: Backup systems are available in case of failure
• Examples: E-commerce websites, banking systems, emergency services

Security Services

Beyond the CIA Triad, security services provide additional protections for information systems:

Non-repudiation

Prevents sender or receiver from denying a transmitted message. This is crucial for legal and business transactions where proof of sending and receiving is required. Implemented using digital signatures and audit trails.

Authentication

Proves identity of users, systems, or entities. Authentication verifies that someone or something is who or what they claim to be. Methods include passwords, biometrics, tokens, and certificates.

Access Controls

Limits and controls access to resources through identification and authentication. Determines what authorized users can do with resources (read, write, execute, delete).

Accountability

Ensures system managers are accountable to external scrutiny. Requires audit trails to be kept and protected, allowing reconstruction of events and identification of responsible parties.

Threats and Attacks

Types of Security Threats

• Denial of Service (DoS): Attacks that make systems unavailable to legitimate users
• Information Theft: Unauthorized access to sensitive data (may go undetected)
• Malware: Viruses, worms, trojans designed to damage or spy
• Social Engineering: Manipulating people into revealing confidential information
• Insider Threats: Attacks from within the organization
• Advanced Persistent Threats (APTs): Long-term, targeted attacks by sophisticated attackers

Categories of Attacks

Passive Attacks

Passive attacks involve eavesdropping on information without modifying it. They are difficult to detect because the attacker does not alter data or systems.

• Eavesdropping: Intercepting communications
• Traffic Analysis: Studying communication patterns
• Release of Message Contents: Reading sensitive data in transit

Active Attacks

Active attacks involve modification or creation of information. They are easier to detect but can cause significant damage.

• Masquerade: Pretending to be someone else
• Replay: Capturing and retransmitting valid data
• Modification: Alter ing messages or data files
• Denial of Service: Disrupting normal system operation

Security Mechanisms

Security mechanisms are technical controls that implement security services:

Common Security Mechanisms

The Security Triad: People, Process, Technology

Effective security requires all three components:

• People: Security-conscious personnel who follow policies
• Process: Procedures and policies that govern security practices
• Technology: Technical controls that enforce security

Chapter Summary

• Computer Security involves prevention, detection, and reaction to unauthorized actions
• The CIA Triad forms the foundation: Confidentiality, Integrity, and Availability
• Security Services include non-repudiation, authentication, access control, and accountability
• Attacks are categorized as passive (eavesdropping) or active (modification)
• Effective security requires people, process, and technology working together