ABSTRACT
Good and evil coexist in this digital world. Any invention has use and misuse too. While attacks have become common in this cyber world, the role of defenders has become critical. Firewalls play a very vital role when it comes to defense mechanisms. This chapter looks at a basic firewall concept and how it works. In the computer networking world, the firewall sits in front of a server or an organisation to prevent illegal entries or communication that is not authorised to enter. Intrusion detection system (IDS) can be deployed on a single system or to a collection of computers that form a network. IDS can be called a combination of hardware and software to monitor actions in a network, user activity, and lots more. Network-based IDS is to monitor a collection of computers in an organisation. This could be mapped to a security guard monitoring a block of homes in a community.
