Chapter 1 network security concepts and policies

Network Security
Concepts and Policies

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Purpose of Security
• To protect assets!
– Historically done through physical security and closed networks.

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The Network Today
• With the advent of personal computers, LANs, and the wide-open

world of the Internet, the networks of today are more open.

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Basic Security Requirements
• To provide adequate protection of network resources, the

procedures and technologies that you deploy need to guarantee

three things :

– Confidentiality
– Integrity
– Availability of systems and data

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Data, Vulnerabilities, and Countermeasures
• An asset is anything of value to an organization.
• A vulnerability is a weakness in a system or its design

that could be exploited by a threat.
• A threat is a potential danger to information or systems.
• A risk is the likelihood that a particular vulnerability will

be exploited.
• An exploit is an attack performed against a

vulnerability.
• A countermeasure (safeguard) is the protection that

mitigates the potential risk.

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Need for Network Security
• Business goals and risk analysis drive the need for network

security
• Dealing with Risk :
– Reduce
– Limitation/avoidance
– Assurance
– Detection
– Recoverry

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Need for Network Security

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Adversaries, Methodologies, and Classes of Attack
• Adversaries : To defend against attacks on information and

information systems, organizations must begin to define the threat
by identifying potential adversaries. These adversaries can

include the following:
• Nations or states
• Terrorists
• Criminals
• Hackers
• Corporate competitors
• Disgruntled employees
• Government agencies, such as the National Security Agency

(NSA) and the Federal Bureau of Investigations (FBI)
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Adversaries, Methodologies, and Classes of Attack
• Methodologies :
– Step 1. Perform footprint analysis (reconnaissance).
– Step 2. Enumerate applications and operating systems.
– Step 3. Manipulate users to gain access.
– Step 4. Escalate privileges.
– Step 5. Gather additional passwords and secrets.
– Step 6. Install back doors.
– Step 7. Leverage the compromised system.

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Adversaries, Methodologies, and Classes of Attack
Threats Classification
• Enumeration and fingerprinting
• Spoofing and impersonation
• Man-in-the-middle
• Overt and covert channels
• Blended threats and malware
• Exploitation of privilege and trust
• Confidentiality
• Password attacks
• Availability attacks
• Denial of service (DoS)
• Botnet
• Physical security attacks
• Forces of nature

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IP Spoofing Attacks

TCP Three-Way Handshake

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Sequence Prediction

Sequence Number Prediction
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Trust Exploitation

Trust Exploitation

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Confidentiality and Integrity Attacks

Breach of Confidentiality

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Man-in-the-Middle Attacks

IP Source Routing Attack
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Overt and Covert Channels

Overt Channel
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Principles of Secure Network Design
• Defense in depth
• Compartmentalization
• Least privilege
• Weakest link
• Separation and rotation of duties
• Hierarchically trusted components and protection
ã Mediated access
ã Accountability and traceability

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Evaluating and
Managing the
Risk

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Risk Analysis and Management
• Every process of security should first address the following

questions:
• Which are the threats the system is facing?
• Which are the probable threats and what would be their
consequence, if exploited?
• The threat-identification process provides an organization with a

list of threats to which a system is subject in a particular
environment.

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Risk Analysis
ã Quantitative
ã Qualitative

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Building Blocks of Risk Analysis

List of Assets and Their Value
• Assets and their value
• Vulnerabilities
• Threats, their impact, and rate or probability of occurrence

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A Lifecycle Approach to Risk Management

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Security Policies
The three reasons for having a security policy are as follows:
• To inform users, staff, and managers
• To specify mechanisms for security
• To provide a baseline
A properly defined security policy does the following:
• Protects people and information
• Sets the rules for expected behavior
• Authorizes staff to monitor, probe, and investigate

ã Defines the consequences of violations

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Security Policy Components

Components of a Comprehensive Security Policy

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Secure Network Lifecycle Management

Organization-wide Integration of IT Governance, Risk
Management, Compliance

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