SPI firewall for more sophisticated protection

Anton P. | June 23, 2020

SPI (stateful packet inspection) firewall is a sophisticated variant of the traditional firewall. It is an advanced security mechanism, tracking connections and analyzing incoming data packets. In other words, it carefully monitors the state of the network and reviews the TCP and UDP streams. Hence, this combination of insightful data simplifies the process of determining which traffic to label as potentially harmful.

What is a stateful packet inspection?

Stateful packet inspection (or dynamic packet filtering) is a rigorous technology that oversees the state of active connections. Then, it can control the flow of packets according to the collected patterns and specifics.

Let’s illustrate the purpose and function of stateful packet inspection by comparing it to its opponent: stateless one. The latter evaluates the validity of packets by examining the static data like the source and destination. The SPI takes a more in-depth look at the entire context of a given network connection. For instance, it is capable of recognizing patterns of incoming connections. Hence, such analysis assists in the prevention of attacks that work outside the packet level. Overall, stateful packet inspection contributes to creating advanced firewall architecture.

What is the SPI firewall?

SPI firewalls are not that rare: almost all firewalls offer stateful monitoring to some extent. In short, such firewalls examine the state of sessions and reject packets that do not comply with the pre-defined regulations. Such security installments monitor IP, TCP, and UDP header details that travel between the client and the server.

Hence, stateful packet inspection blocks unsolicited connection requests from reaching your device. If you dodge external requests and random packets, you can avoid establishing undesirable communications. The firewall’s rule set can clearly state which external servers can initiate successful connections. Furthermore, it will guarantee that verified returning connections won’t face any obstacles.

How do SPI firewalls work?

Stateful packet inspection firewalls have an incredible memory. They gather information about each connection for determining the packet credibility in the future. So, the collected data is relevant when crafting guidelines or regulations. SPI firewalls can analyze the context of each connection by establishing rules and regulating the flow of packets.

In simple terms, the context refers to the IP addresses, the final packet received, packet length, etc. Another important concept is a state. It is a vital factor, allowing the SPI firewall to filter packets. Such firewalls also perform back and forth negotiations known as a three-way handshake. This phenomenon refers to the introduction that new connections need to make. Only then can the incoming packets move on to the successful connection.

Pros of an SPI firewall

  • Currently, stateful inspection firewalls are the industry-standard tools for protecting networks. They provide the perfect balance between the performance of packet filtering and security overall.
  • The most critically-acclaimed feature of SPI firewalls is their attention to the state and context of the incoming connections.
  • SPI firewalls are the most modern blockages capable of carefully filtering all packets and the header’s fields at the IP and TCP layers.

Cons of an SPI firewall

  • Stateful firewalls follow an extensive routine to provide more security. Hence, they require more processing power. Nonetheless, experts introduce workarounds for this by applying advanced algorithms. These overcome the excessive use of CPU cycles by dividing the processes. So, a well-designed SPI firewall should not differ too much in its performance from regular firewalls.
  • While the provided protection is stable and reliable, it is necessary to install the latest software releases. Vulnerabilities can allow hackers to compromise your connection if you do not perform regular updating.
  • Crooks can still trick such firewalls into permitting devious connections. So, while they are valuable mechanisms, it is best to use a combination of security tools.

Other security tips to follow

A firewall remains an essential tool to have in your digital arsenal. However, the craftsmanship of cyberattacks has evolved alongside security tools. Hence, an SPI firewall should be one of the components that warrant comprehensive protection.

  • Anti-virus software. It is the best defense mechanism against malware and devastating parasites.
  • A VPN. It is the instrument that allows privacy-concerned netizens to mask their IP addresses and encrypt data transmissions. Choose not to leave digital footprints while browsing.
  • Safe browsing practices. Be vigilant enough to avoid common online scams and traps set by perpetrators. New threats emerge regularly, and you need to stay one step ahead of the hackers.
  • Agree to install regular updates. It is always best to use an operating system or an application that functions with the latest features. While it might be tempting to push those update notifications away, their impact on devices is tremendous. Outdated versions contain unpatched flaws that hackers can exploit for financial gain or malicious attacks.
Anton P.

Anton P.

Former chef and the head of Atlas VPN blog team. He's an experienced cybersecurity expert with a background of technical content writing.



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