A firewall is a network security device or software that acts as a barrier between your computer or network and the internet. It monitors incoming and outgoing network traffic and filters it based on a set of rules.
How Firewalls Work
Packet Inspection: Firewalls examine each network packet, which is a unit of data transmitted over a network.
Rule Evaluation: The firewall compares the packet's information, such as source and destination addresses, ports, and protocols, against a set of predefined rules.
Decision Making: Based on the rules, the firewall decides whether to allow, block, or modify the packet.
Types of Firewalls
Software Firewall: A software program installed on your computer or network device.
Hardware Firewall: A dedicated physical device that sits between your network and the internet.
Stateful Firewall: Keeps track of the state of network connections, allowing authorized traffic to pass through while blocking unauthorized attempts.
Stateless Firewall: Examines each packet individually without considering the context of previous packets.
Packet Filtering Firewall: Examines the header information of each packet to decide whether to allow or block it.
Application Firewall: Examines the content of network traffic at the application layer, providing more granular control.
Firewall Rules
Firewall rules define the criteria for allowing or blocking network traffic. Common rules include:
Allow specific ports: Allow traffic to and from specific ports, such as those used for web browsing (port 80) or email (port 25).
Block specific IP addresses: Block traffic from known malicious IP addresses.
Allow traffic from specific networks: Allow traffic from trusted networks, such as your home or office network.
Block specific applications: Block traffic for certain applications or services.
By using a firewall, you can help protect your computer or network from unauthorized access and malicious attacks.
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