Firewall – Concept, types of firewall and how it works

We explain what a firewall is, what it is for and how this system works. Also, the types that exist and the Windows firewall.

The firewall is a first defense step in the world of computer networks.

What is a firewall?

In computing, and more specifically in telecommunications, it is understood by firewall (in English) or firewall to a system or device capable of allowing, limiting, encrypting or decoding communication traffic between a computer (or a local network) and the rest of the Internet, preventing unauthorized users or systems from having access.

A firewall can be either physical or digital, that is, a device or a piece of software, and in both cases It is only a first defense step in the world of computer networks, essential but not sufficient to guarantee security against cyber attacks and third-party intrusions.

This type of technology borrowed its name from the fire prevention mechanism that is usually applied in green areas or vulnerable buildings, and that consists of a wall or a vacant area, free of any flammable content, which limits the indefinite expansion of the fire in case of fire.

The precursors of the firewall emerged during the 1980s, when the Internet was still a recent field of knowledge and the margin of damage possible through the hack or cyber terrorism.

Since the first massive cyberattacks by digital viruses and worms in the early following decade, digital protection has been expanded and perfected, at the rate that new pieces of harmful software appear, known as malware.

What is a firewall for?

A firewall prevents the entry or exit of unauthorized communications.

A firewall serves, simply put, to interrupt unauthorized or suspicious connections between a computer system or computer, and the Internet. This cuts off remote communication between malicious users (hackers) and the local system, or between pieces of malware stealthily installed on the system and outside of it, thus preventing it from operating as a spearhead in the cyber invasion.

It is, therefore, a guard who prevents the entry or exit of unauthorized or suspicious communications, based on criteria of discernment that are updated from time to time.

How does a firewall work?

Firewalls distinguish between allowed and dangerous or suspicious connections, based on different procedures, such as:

  • Firewall policies. Using IP numbers and other identification systems, the firewall suspends any communication request that does not come from the internal network or from the system itself, disguising all internal resources behind its own IP, so that no one can monitor them from within. outside.
  • Content filtering. Through a system of exclusion rules in which the user can have the last word, the firewall distinguishes between problematic, suspicious or unsafe content, and those that are left to the user’s discretion. Thus, access to entire web pages or servers can be blocked as a precaution.
  • Antimalware services. Many firewalls have built-in virus and malware definitions provided by various defensive programs, in order to also help keep these malicious programs from spreading.
  • IPR services. The Deep Packet Inspection (IPP or DPI) procedures are called this: Deep Package Inspection), which adds a second layer of security to the system, reviewing the deep content of the information packets received.

Types of firewall

The personal firewall is chosen and installed by the user.

There are the following types of firewall:

  • Gateway application level. Applies only to specific applications considered risky, such as FTP servers or free exchange of information between users (P2P). It is usually very efficient, but it imposes a drain on system resources.
  • Walkway level circuit. Monitors the establishment of TCP or UDP connections through security sessions.
  • Network layer firewall. It operates based on the inspection of IP addresses and the exchange of IP packets, using alternate data such as the MAC address.
  • Application layer firewall. It already operates on the basis of applications, controlling its way of reaching the Internet, for example, through Proxys.
  • Personal firewall. Firewalls chosen by the user and installed in the system to meet the individual requirements of use of the system.

Windows firewall

Microsoft’s famous operating system, called Windows, includes firewall software among its self-defense options. This option was included in the System Security Center from its version XP Service Pack 2, seeking to offer greater control and defense of the stability of the system for its users.

This firewall is updated along with the other Windows applications to keep up with cyber threats, and activates automatically unless there is some other antivirus or firewall software that has the connection management privileges, in which case the Windows firewall will remain disabled.