Firewall

Given the exponential growth of virtual systems, vulnerabilities in systems have also increased, affecting both home users and users of managed or unmanaged VPS services, as well as other more specialized services. Therefore, security is one of the main concerns. In this regard, a firewall is a network security system that restricts both incoming and outgoing traffic, as well as internal traffic. 

This tool is one of the basic security mechanisms that every system must implement to keep its information secure. As a preventive system, it can reduce vulnerabilities and prevent greater damage from cyberattacks. It is important to note that this security measure is adaptable to both home systems and VPS. 

What is a Firewall?

A firewall is dedicated software or hardware that selectively restricts access to a system. Its primary purpose is to prevent malicious activity by restricting unauthorized activities on the conventional network or VPS server. 

In this sense, firewalls can be considered as barriers that stop the flow of activity, much like fire doors, from which they derive their name. This restriction mechanism allows for the secure management of web traffic and stops the spread of threats, serving as an additional protective measure for VPS servers. 

Firewalls perform checks based on pre-programmed parameters to restrict certain types of activity. Additionally, some firewalls can monitor traffic and connections to verify what is permitted by the VPS server or the home device. 

Due to this broad functionality, firewalls are security tools for different types of user access. Their primary locations are within the network, on user computers, and at other connection points. In this regard, their operability also stands out in a VPS service to control the incoming and outgoing traffic of the VPS server. 

Types of Firewalls

Firewalls are categorized based on the types of functions they perform. Their basic filtering methods include connection tracking, filtering rules, and audit logs. These methods give rise to various specific types of firewalls, of which we will describe some of the most commonly used, both in home systems and VPS.

1. Static Packet Filtering Firewall

Also known as stateless inspection firewalls, these operate at the OSI network layer. They provide basic filtering by checking individual data packets sent over the network. They evaluate the source and destination of the packets. Since they do not inspect previously accepted connections, they repeat the checking process each time they receive information. 

This type of filtering is based on IP addresses, ports, and packet protocols. Rules are established through a manually created access control list and are characterized by their rigidity when applied. 

Due to these characteristics, this firewall requires constant checks for proper functioning and is especially suitable for small networks that can manage it. 

1. Circuit-Level Gateway Firewall

Circuit-level gateways operate at the session layer. These firewalls check the functionality of packets during the connection attempt. Once this procedure is completed, the firewall does not go any further. They are similar to proxy firewalls.

1. Stateful Inspection Firewall

Also known as dynamic packet filtering firewalls, they have the ability to monitor ongoing connections and remember previously inspected packets. These firewalls can monitor multiple connection layers, including the application layer. 

They also block or restrict traffic based on technical properties, such as specific packet protocols, IP addresses, and ports. However, they also monitor and filter the state of connections. This firewall updates filtering rules based on events recorded earlier in the state table by the filtering router.

The filtering parameters are established in the configuration of the device and the firewall. Additionally, having state tables allows the firewall to "learn" from previous interactions, meaning that types of traffic that caused issues in the past will be restricted in the future. Due to this flexibility and capacity, it is one of the most widely used methods.

1. Proxy Firewall

These application-level firewalls are unique in that they read and filter application protocols. In this sense, they combine application-level inspection or packet inspection with state inspection in their operation. 

The type of filtering they perform is based on application-level data, rather than basic IP addresses, ports, and packet protocols like packet-based firewalls. By reading and understanding FTP, HTTP, DNS, and other protocols, they can conduct more in-depth investigations and cross-filter different aspects of data.

Despite the significant advantages they offer in filtering, they often interfere with incoming data that is not genuinely harmful, slowing down system functionality. 

1. Next-Generation Firewall (NGFW)

This type of firewall combines the functions of a traditional firewall with intrusion prevention systems. They are designed to identify and prevent specific threats, such as advanced malware. They are used by companies and sophisticated networks to provide a more comprehensive security solution against the most common threats they face. 

Through the mechanisms described, firewalls allow for control over network processes and ensure a certain level of security. In addition to these protective functionalities, such as preventing the infiltration of malicious agents, firewalls are also used by parental control systems to block access to certain web content. They are also used as restriction mechanisms for web browsing in workplaces, enabling employers to prevent employees from accessing specific web content. Similarly, firewalls are used to manage a controlled internal network at a national level. That is, a government may determine that access to certain web content that opposes its political interests is blocked, as occurs in China.

In summary, the firewall system is a powerful tool that enhances the potential of using virtual systems and environments by providing prevention mechanisms that ensure the security of operations, such as those on VPS servers. Although Linux VPS servers already have a security system in place, it is important to consider firewall configuration on the VPS for protection. However, like any other security system, it is essential to adapt it to the specific needs of our systems and manage its proper functioning; thus, it is important to manage it from the VPS control panel, whether for a managed VPS service or an unmanaged VPS service.