Firewall

A firewall is a network security device that is used to monitor and filter incoming and outgoing network traffic. Firewalls are designed to prevent unauthorized access to a network or an endpoint by blocking traffic that is considered suspicious or malicious.

Subfields of Firewall

• Network Firewall: a type of firewall that is deployed at the perimeter of a network to monitor and filter incoming and outgoing network traffic. Network firewalls can be hardware-based or software-based and can be configured to enforce various security policies.
  
  
• Host-based Firewall: a type of firewall that is deployed on an endpoint to monitor and filter incoming and outgoing traffic. Host-based firewalls can be used to enforce security policies for individual endpoints, such as desktops, laptops, and mobile devices.
  
  
• Application Firewall: a type of firewall that is designed to monitor and filter network traffic based on the application protocol. Application firewalls can be used to enforce security policies for specific applications, such as web browsers, email clients, and file-sharing software.
  
  
• Next-Generation Firewall (NGFW): a type of firewall that incorporates advanced features, such as intrusion prevention, application control, and deep packet inspection. NGFWs are designed to provide more granular control over network traffic and to detect and prevent a wider range of security threats.
  
  
• Unified Threat Management (UTM): a type of firewall that combines multiple security functions, such as firewalling, antivirus, intrusion prevention, and content filtering, into a single device. UTMs are designed to simplify security management and to provide comprehensive protection against a range of security threats.
  
  
• Packet-filtering Firewall: a type of network firewall that examines the header information of packets and blocks or allows them based on certain criteria, such as source IP address, destination IP address, and port number.
  
  
• Circuit-level Firewall: a type of network firewall that operates at the transport layer of the OSI model and monitors TCP handshaking between packets to determine whether a requested session is legitimate.
  
  
• Proxy Firewall: a type of network firewall that uses a proxy server to filter traffic. When a client behind the firewall requests a resource from the Internet, the proxy server retrieves the resource on behalf of the client and filters the traffic before passing it along.
  
  
• Stateful Firewall: a type of network firewall that keeps track of the state of network connections and allows only legitimate packets that belong to established sessions.
  
  
• Virtual Private Network (VPN) Firewall: a type of network firewall that is specifically designed to secure VPN connections. VPN firewalls can provide encryption and authentication for VPN traffic.
  
  

Available Software Firewalls

• Windows Firewall: built-in firewall software that is included with Microsoft Windows operating systems.
  
  
• ZoneAlarm: a popular software firewall that provides inbound and outbound protection.
  
  
• Norton Personal Firewall: a software firewall that provides intrusion protection and privacy protection.
  
  
• Comodo Firewall: a free firewall software that provides comprehensive protection against inbound and outbound threats.
  
  

Available Hardware Firewalls

• Cisco ASA: a hardware firewall that provides advanced security features, such as VPN and intrusion prevention.
  
  
• Juniper Networks SRX Series: a hardware firewall that provides advanced threat prevention and application visibility and control.
  
  
• Fortinet FortiGate: a hardware firewall that provides integrated threat management, VPN, and application control.
  
  
• SonicWall: a hardware firewall that provides network security, VPN, and wireless access point protection.