Guide to Network Defense and Countermeasures Second Edition Chapter 5 Virtual Private Network (VPN) Concepts

Objectives Explain basic VPN concepts Describe encapsulation in VPNs Describe encryption in VPNs Describe authentication in VPNs Summarize the advantages and disadvantages of VPNs Guide to Network Defense and Countermeasures, Second Edition

Understanding VPN Concepts Virtual Private Network (VPN) enables computers to Communicate securely over insecure channels Exchange private encrypted messages that others cannot decipher Guide to Network Defense and Countermeasures, Second Edition

What VPNs Are VPN Endpoints Virtual network connection Uses the Internet to establish a secure connection Secure tunnel Extends an organization’s network Endpoints Specified computers, users, or network gateways Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Why Establish a VPN? Business incentives driving VPN adoption VPNs are cost-effective VPNs provide secure connection for remote users Contractors Traveling employees Partners and suppliers VPN Components VPN server or host Configured to accept connections from clients VPN client or guest Endpoints connecting to a VPN Guide to Network Defense and Countermeasures, Second Edition

Why Establish a VPN? (continued) VPN Components Tunnel Connection through which data is sent VPN protocols Sets of standardized communication settings Used to encrypt data sent along the VPN Types of VPNs Site-to-site VPN Gateway-to-gateway VPN Client-to-site VPN Remote access VPN Guide to Network Defense and Countermeasures, Second Edition

Why Establish a VPN? (continued) Hardware versus software VPNs Hardware-based VPNs Connect one gateway to another Routers at each network gateway encrypt and decrypt packets VPN appliance Designed to serve as VPN endpoint Join multiple LANs Benefits Scalable Better security Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Why Establish a VPN? (continued) Hardware versus software VPNs (continued) Software-based VPNs Integrated with firewalls Appropriate when participating networks use different routers and firewalls Benefits More cost-effective Offer maximum flexibility Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Why Establish a VPN? (continued) VPN combinations Combining VPN hardware with software adds layers of network security One useful combination is a VPN bundled with a firewall VPNs do not eliminate the need for firewalls Provide flexibility and versatility Guide to Network Defense and Countermeasures, Second Edition

Why Establish a VPN? (continued) VPN combinations (continued) Points to consider when selecting VPNs Compatibility Scalability Security Cost Vendor support Guide to Network Defense and Countermeasures, Second Edition

VPN Core Activity 1: Encapsulation Core set of activities Encapsulation Encryption Authentication Encloses a packet within another That has different IP source and destination Protects integrity of the data Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Understanding Tunneling Protocols Point-to-Point Tunneling Protocol (PPTP) Used when you need to dial in to a server with a modem connection On a computer using an older OS version Encapsulates TCP/IP packets Header contains only information needed to route data from the VPN client to the server Uses Microsoft Point-to-Point Encryption (MPPE) Encrypt data that passes between the remote computer and the remote access server L2TP uses IPSec encryption More secure and widely supported Guide to Network Defense and Countermeasures, Second Edition

Understanding Tunneling Protocols (continued) Layer 2 Tunneling Protocol (L2TP) Provides better security through IPSec IPSec enables L2TP to perform Authentication Encapsulation Encryption Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Understanding Tunneling Protocols (continued) Secure Shell (SSH) Provides authentication and encryption Works with UNIX-based systems Versions for Windows are also available Uses public-key cryptography Socks V. 5 Provides proxy services for applications That do not usually support proxying Socks version 5 adds encrypted authentication and support for UDP Guide to Network Defense and Countermeasures, Second Edition

IPSec/IKE Internet Protocol Security (IPSec) Characteristics Set of standard procedures Developed by the Internet Engineering Task Force (IETF) Enables secure communications on the Internet Characteristics Works at layer 3 Can encrypt an entire TCP/IP packet Originally developed for use with IPv6 Provides authentication of source and destination computers Guide to Network Defense and Countermeasures, Second Edition

IPSec/IKE (continued) Widely supported Security Association (SA) Relationship between two or more entities Describes how they will use security services to communicate Used by IPSec to track all the particulars of a communication session SAs are unidirectional Guide to Network Defense and Countermeasures, Second Edition

IPSec/IKE (continued) Components Internet Security Association Key Management Protocol (ISAKMP) Internet Key Exchange (IKE) Oakley IPSecurity Policy Management IPSec Driver IPSec core components Authentication Header (AH) Encapsulation Security Payload (ESP) Guide to Network Defense and Countermeasures, Second Edition

IPSec/IKE (continued) Authentication Header (AH) Provides authentication of TCP/IP packets Ensures data integrity Packets are signed with a digital signature Adds a header calculated by the values in the datagram Creating a messages digest of the datagram AH in tunnel mode Authenticates the entire original header Places a new header at the front of the original packet AH in transport mode Authenticates the payload and the header Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

IPSec/IKE (continued) Encapsulation Security Payload (ESP) Provides confidentiality for messages Encrypts different parts of a TCP/IP packet ESP in tunnel mode Encrypts both the header and data part of each packet Data cannot pass through a firewall using NAT ESP in transport mode Encrypts only data portion of the packet Data can pass through a firewall IPSec should be configured to work with transport mode Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

VPN Core Activity 2: Encryption Process of rendering information unreadable by all but the intended recipient Components Key Digital certificate Certification Authority (CA) Key exchange methods Symmetric cryptography Asymmetric cryptography Internet Key Exchange FWZ Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Encryption Schemes Used by VPNs Triple Data Encryption Standard (3DES) Used by many VPN hardware and software 3DES is a variation on Data Encryption Standard (DES) DES is not secure 3DES is more secure Three separate 64-bit keys to process data 3DES requires more computer resources than DES Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Encryption Schemes Used by VPNs (continued) Secure Sockets Layer (SSL) Developed by Netscape Communications Corporation Enables Web servers and browsers to exchange encrypted information Characteristics Uses public and private key encryption Uses sockets method of communication Operates at network layer (layer 3) of the OSI model Widely used on the Web Only supports data exchanged by Web-enabled applications Unlikely to replace IPSec Guide to Network Defense and Countermeasures, Second Edition

Encryption Schemes Used by VPNs (continued) Secure Sockets Layer (SSL) (continued) Steps Client connects to Web server using SSL protocol Two machines arrange a “handshake” process Client sends its preferences for encryption method, SSL version number, and a randomly generated number Server responds with SSL version number, its own cipher preferences, and its digital certificate Client verifies date and other information on the digital certificate Client generates and send a “pre-master” code Guide to Network Defense and Countermeasures, Second Edition

Encryption Schemes Used by VPNs (continued) Secure Sockets Layer (SSL) (continued) Steps Server uses its private key to decode pre-master code Generates a master secret key Client and server use it to generate session keys Server and client exchange messages saying handshake is completed SSL session begins Guide to Network Defense and Countermeasures, Second Edition

VPN Core Activity 3: Authentication Identifying a user or computer as authorized to access and use network resources Types of authentication methods used in VPNs IPSec MS-CHAP Both computers exchange authentication packets and authenticate one another VPNs use digital certificates to authenticate users Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Kerberos Authentication system Developed at the Massachusetts Institute of Technology (MIT) Authenticates the identity of network users Authentication by assertion Computer that connects to a server and requests services acts on behalf of an approved user Guide to Network Defense and Countermeasures, Second Edition

Guide to Network Defense and Countermeasures, Second Edition

Kerberos (continued) Advantages Disadvantages Passwords are not stored on the system They cannot be intercepted Has a lower “network overhead” than a Public Key Infrastructure (PKI) Handy for single sign-on (SSO) Disadvantages AS (KDC) is a single point of failure for Kerberos Guide to Network Defense and Countermeasures, Second Edition

Advantages and Disadvantages of VPNs Guide to Network Defense and Countermeasures, Second Edition

Summary VPNs do not make use of dedicated leased lines VPNs send data through a secure tunnel that leads from one endpoint to another VPNs keep critical business communications private and secure VPN components VPN servers VPN clients Protocols Guide to Network Defense and Countermeasures, Second Edition

Summary (continued) VPN types Site-to-site Client-to-site Encapsulation encloses one packet within another Conceals the original information VPN protocols Secure Shell (SSH) Socks version 5 Point-to-Point Tunneling Protocol (PPTP) Layer 2 Tunneling Protocol (L2TP) Guide to Network Defense and Countermeasures, Second Edition

Summary (continued) IPSec/IKE Encryption makes the contents of the packet unreadable Authentication ensures participating computers are authorized users Kerberos: strong authentication system VPN advantages High level of security at low cost VPN disadvantages Can introduce serious security risks Guide to Network Defense and Countermeasures, Second Edition