Firewalls
Introduction
This lecture discusses about security mechanisms in the Internet namely Firewall . In brief, It's a configuration of routers and networks placed between an organization's internal internet and a connection to an external internet to provide security. In other words, Firewall is a mechanism to provide limited access to machines either from the outside world to internal internet or from internal world to outside world. By, providing these security mechanisms, we are increasing the processing time before one can access a machine. So, there is a trade-off between security and ease of use. A firewall partitions an internet into two regions, referred to informally as the inside and outside. __| | _________ Firewall
______________________ | | ____________________
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| | | | | |
| Rest of Internet |________ | |_____ | Intranet |
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|_____________________ | | | |___________________|
|_|
Outside Inside
Security Lapses
- Vulnerable Services - NFS : A user should not be allowed to export certain files to the outside world and from the outside world also, someone should not be allowed to export our files.
- Routing based attacks : Some kind of ICMP message should not be allowed to enter my network. e.g.. Source routing and change route ICMP's.
- Controlled access to our systems : e.g.. Mail server and web pages should be accessible from outside but our individual PC's should not be accessible from the outside world.
- Authentication : Encryption can be used between hosts on different networks.
- Enhanced Privacy : Some applications should be blocked. e.g.. finger ...
- PING & SYN attack : Since these messages are send very frequently, therefore you won't be able to do anything except reply to these messages. So, I should not allow these messages to enter my network.