A firewall is a computer security device that blocks unauthorized access to a computer network by filtering traffic. Firewalls are a type of network security appliance.
They are typically used to protect computers and networks from unauthorized access, interception, or destruction of data. .
A firewall can be classified by its function:
1. Network Address Translation (NAT) firewalls: NAT firewalls allow several internal IP addresses to map to one external IP address.
This allows internal users to access the Internet through the firewall while protecting the internal network from outside attacks.
2. Connection Security Firewalls: Connection Security Firewalls (CSPs) are a type of firewall that inspects all traffic before allowing it to enter the network.
CSPs use a set of rules to decide whether to allow a connection to pass or not.
3. Application Security Firewalls: Application Security Firewalls (ASF) are a type of firewall that inspects and blocks attacks against applications.
ASF can help protect against attacks that exploit weaknesses in the applications themselves, or in the way that the applications are deployed.
4. Stateful Firewalls: Stateful Firewalls are a type of firewall that keep track of the current and past traffic flowing through the firewall.
This allows the firewall to block traffic that is known to be malicious.
5. Web Application Firewalls: Web Application Firewalls (WAFs) are a type of firewall that protects web applications from attack.
WAFs can block attacks that exploit vulnerabilities in the web applications themselves, or in the way that the web applications are deployed.
6. Intrusion Detection and Prevention Systems: Intrusion Detection and Prevention Systems (IDS/IPS) are a type of firewall that monitors network traffic for signs of suspicious activity.
If suspicious activity is detected, the IDS/IPS can take action, such as blocking the traffic or reporting the activity to a security team.
7. Advanced Firewalls: Advanced Firewalls are a type of firewall that can do more than just block traffic.
Advanced Firewalls can also protect the computers and networks from attack, and can monitor and manage the network traffic.
Firewalls can be classified by their functionality:
The main purpose of a firewall is to protect computer systems and networks from unauthorized access and damage. A firewall can do this by filtering traffic before it enters the network, by monitoring traffic to and from the network, or by blocking traffic that is known to be malicious.
