Information Security: Firewall (Definitions)

"A device or program that blocks outsiders from accessing a computer connected to the Internet. Some firewalls also monitor data traffic outbound from a computer or network." (Andy Walker, "Absolute Beginner’s Guide To: Security, Spam, Spyware & Viruses", 2005)

"Software or devices that examine network traffic so that it may restrict access to network resources to unauthorized users." (Tom Petrocelli, "Data Protection and Information Lifecycle Management", 2005)

"A network security system used to monitor and restrict external and internal traffic." (Robert McCrie, "Security Operations Management" 2nd Ed., 2006)

"A firewall is part of a computer network or system that is designed to block unauthorized access over communications lines." (Michael Coles & Rodney Landrum, , "Expert SQL Server 2008 Encryption", 2008)

"A system level networking filter that restricts access based on, among other things, IP address. Firewalls form a part of an effective network security strategy. See Firewalls." (MongoDb, "Glossary", 2008)

"A piece of software that filters incoming and outgoing network traffic and stops messages that violate the rules that define allowable traffic." (Jan L Harrington, "Relational Database Design and Implementation" 3rd Ed., 2009)

"A computer system placed between the Internet and an internal subnet of an enterprise to prevent unauthorized outsiders from accessing internal data." (Paulraj Ponniah, "Data Warehousing Fundamentals for IT Professionals", 2010)

"A combination of specialized hardware and software set up to monitor traffic between an internal network and an external network (i.e. the Internet). Its primary purpose if for security and is designed to keep unauthorized outsiders from tampering with or accessing information on a networked computer system." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

"Hardware and software that blocks outsiders from accessing your data and creates a secure environment for your data while permitting those with authorization, such as employees, to access information as needed." (Gina Abudi & Brandon Toropov, "The Complete Idiot's Guide to Best Practices for Small Business", 2011)

"System or group of systems that enforces an access-control policy between two networks." (Linda Volonino & Efraim Turban, "Information Technology for Management" 8th Ed., 2011)

"A device that is used to control access between two networks. Typically used when connecting a private network to the Internet as a way of protecting and securing the internal network from threats, hackers, and others. Also used when connecting two private networks (e.g., supplies, partners, etc.)." (Bill Holtsnider & Brian D Jaffe, "IT Manager's Handbook" 3rd Ed., 2012)

"A network access control system that uses rules to block or allow connections and data transmission between a private network and an untrusted network, such as the Internet." (Mark Rhodes-Ousley, "Information Security: The Complete Reference" 2nd Ed., 2013)

"A form of protection that allows one network to connect to another network while maintaining some amount of protection." ( Manish Agrawal, "Information Security and IT Risk Management", 2014)

"Software or hardware designed to control traffic. A network-based firewall is typically hardware, and it controls traffic in and out of a network. A host-based firewall is software installed on individual systems and it controls traffic in and out of individual systems." (Darril Gibson, "Effective Help Desk Specialist Skills", 2014)

"A a network security measure designed to filter out undesirable network traffic." (Weiss, "Auditing IT Infrastructures for Compliance" 2nd Ed., 2015)

"A gateway machine and its software that protects a network by filtering the traffic it allows" (Nell Dale & John Lewis, "Computer Science Illuminated" 6th Ed., 2015)

"A security barrier on your computer or network that controls what traffic is allowed to pass through." (Faithe Wempen, "Computing Fundamentals: Introduction to Computers", 2015)

"Software that blocks hackers from accessing a computer by closing unnecessary services and ports." (Faithe Wempen, "Computing Fundamentals: Introduction to Computers", 2015)

"A network device designed to selectively block unauthorized access while permitting authorized communication to devices within a subnetwork." (O Sami Saydjari, "Engineering Trustworthy Systems: Get Cybersecurity Design Right the First Time", 2018)