The document describes a firewall called Net Defender that was developed by students to secure personal computers from unauthorized internet access. It discusses security issues on the internet, common attacks like DDoS and port scanning, and how firewalls work using techniques like packet filtering, address filtering and port blocking. It provides details of Net Defender's interface, features like adding rules and a port scanner, and how it prevents attacks and vulnerabilities using these techniques. Future work mentioned includes improving the analysis and extending it to model more complex firewalls.

1. Net Defender By: Y.Hemanth Kumar M.Krishna Reddy CH.Mahesh Tuesday, May 2, 2001 SC 546

8. Example of DoS attack: Intruder Target ICMP request with spoofed IP of target

9. Example of DoS attack: Intruder Target Flood Target with replies

11. Net Defenders

13. Net defender Problem Statement Developing a simple Firewall for securing Personal Computer from unauthorized access through Internet or network by novice and advanced users.

14. Objective of Net defender Net Defender software is being designed keeping in mind a novice user (those who knows very less about networking or computers). We had laid a great deal of stress in providing a sound user interface so that a general user should learn how to use and control this firewall in simple and easy steps.

17. Main Screen Firewall has a simple user interface that gives you instant access to all your security features

18. Add Rule : This dialog box will help in adding new rules to Firewall. To create a rule, you must first specify the kind of traffic that should be affected by the rule. There are several different characteristics of traffic, each of which you can use to specifythe kind of traffic that you want to control .

20. Well-known ports used by TCP Port Protocol Description 7 Echo Echoes a received datagram back to the sender 9 Discard Discards any datagram that is received 11 Users Active users 13 Daytime Returns the date and the time 17 Quote Returns a quote of the day 19 Chargen Returns a string of characters 20 FTP, Data File Transfer Protocol (data connection) 21 FTP, Control File Transfer Protocol (control connection) 23 TELNET Terminal Network 25 SMTP Simple Mail Transfer Protocol 53 DNS Domain Name Server 67 BOOTP Bootstrap Protocol 79 Finger Finger 80 HTTP Hypertext Transfer Protocol 111 RPC Remote Procedure Call