tailieunhanh - Lecture notes on Computer and network security: Lecture 19 - Avinash Kak

Lecture 19, proxy-server based firewalls. After studying this chapter you will be able to understand: The SOCKS protocol for anonymizing proxy servers, socksifying application clients, the dante SOCKS server, Perl and Python scripts for accessing an internet server through a SOCKS proxy, squid for controlling access to web resources (and for web caching),. | Lecture 19: Proxy-Server Based Firewalls Lecture Notes on “Computer and Network Security” by Avi Kak (kak@) March 24, 2016 10:03pm c 2016 Avinash Kak, Purdue University Goals: • The SOCKS protocol for anonymizing proxy servers • Socksifying application clients • The Dante SOCKS server • Perl and Python scripts for accessing an internet server through a SOCKS proxy • Squid for controlling access to web resources (and for web caching) • The Harvest system for information gathering, indexing, and searching • How to construct an SSH tunnel through a web proxy CONTENTS Section Title Page Firewalls in General (Again) 3 SOCKS 7 SOCKS4 versus SOCKS5 10 Interaction Between a SOCKS Client and a SOCKS Server 11 Socksifying a Client-Side Application 16 Dante as a SOCKS Proxy Server 19 Configuring the Dante Proxy Server 22 Configuring SOCKS Clients 30 Anonymity Check 33 Perl and Python Scripts for Accessing an Internet Server through a danted Proxy 34 The SQUID Proxy Server 47 Starting and Stopping the Squid Proxy Server 50 The Squid Cache Manager 55 Configuring the Squid Proxy Server 62 HARVEST: A System for Information Gathering and Indexing 72 What Does Harvest Really Do? 73 Harvest: Gatherer 75 Harvest: Broker 78 How to Create a Gatherer? 79 How to Create a Broker? 88 Constructing an SSH Tunnel Through an HTTP Proxy 93 Homework Problems 98 Computer and Network Security by Avi Kak Lecture 19 : FIREWALLS IN GENERAL (AGAIN) • To expand on what was mentioned at the beginning of Lecture 18, firewalls can be designed to operate at any of the following three layers in the TCP/IP protocol stack: – the Transport Layer (example: packet filtering with iptables) – the Application Layer (example: HTTP Proxy) – the layer between the Application Layer and the .