What Is an SPI Firewall?

One of the main things that keeps us safe from attacks and viruses that come through the Internet is a firewall. But not all of them are just as strong and safe. You could choose the SPI firewall as one of your options. Let’s see how it works and what it’s like.

What Is an SPI Firewall
What Is an SPI Firewall

What’s the SPI?

Stateful packet inspection, also called “dynamic packet filtering,” is a technology that checks incoming data packets to see if they match connections that are already open. Then, it decides whether to let them pass through the firewall or not.

As we talked about in this blog post about IP fragmentation, devices send data in pieces called “packets” to make it easier for the other end to process. Several packets could be made out of a single large data unit. But hackers could change these packets in a way that hurts the server that receives them. So, the SPI firewall checks to see if these packets are real and match up with a connection that has already been made. It throws away packets that don’t belong to a known connection, making a breach less likely.

What does an SPI firewall mean?

An SPI (stateful packet inspection) firewall keeps you safe by comparing new packets to connections that are already open.

A stateless firewall, on the other hand, checks things like source and destination addresses, which don’t change. It doesn’t take the connection traffic of the packet into account. It uses the same rules for each packet and has no information about its connection. You can’t change these firewalls so that they can open and close connections. They also don’t check if packets are real and can’t tell if they come from a real IP. So, they are not as safe as SPI firewalls, but most of the time they are faster.

Also read : What Is the Purpose of a Firewall?

Stateless Packet Inspection’s Weak Points

In a Security Pro News article from February 2002, written by Jay Fougere, he says that stateless IP filters are good at routing traffic and don’t use up many computer resources, but they are very bad for network security. Stateless filters don’t authenticate packets, can’t be set up to open and close connections in response to certain events, and make it easy for hackers to get into a network using IP spoofing, which is when incoming packets have a fake IP address that makes the firewall think it’s from a trusted source.

How do SPI firewalls works ?

An SPI firewall can remember the properties of each connection and use this information to figure out if a packet is legitimate. It keeps the information it gets from looking at the packets and making rules. So, it can see the bigger picture of a packet, not just what’s inside.

Because of this memory, the SPI firewall doesn’t have to look at every packet in detail, so it works faster than deep packet inspection (DPI). The second one takes the packets apart to see if they are put together correctly and if they contain any bad code. DPI is used for many things, such as network management, security, data mining, and censoring the internet. It gives you safety at the cost of speed.

Also read : How To Turn on The Firewall in Windows 10

How an SPI Firewall controls who can get into a network

An SPI firewall keeps track of the identifiers of all the packets its network sends, so when an incoming packet tries to connect to the network, the firewall can tell if it’s a response to a packet sent from its network or if it’s a new packet that hasn’t been asked for. An SPI firewall can use an access control list, a database of trusted entities, and the permissions those entities have to get on the network. The SPI firewall can check the ACL to see if a packet came from a trusted source and, if it did, to figure out where it can be sent in the network.

Taking Action on Suspicious Traffic

The SPI firewall can be set up to drop any packets sent from sources not listed in the ACL. This helps prevent a denial-of-service attack, in which an attacker floods the network with incoming traffic to use up its resources and make it unable to respond to legitimate requests. In the article “Security: Comparing NAT, Static Content Filtering, SPI, and Firewalls” on Netgear’s website, it says that SPI firewalls can also look at packets for characteristics used in known hacking exploits, like DoS attacks and IP spoofing, and drop any packets that it thinks could be harmful.

Also read : How to Disable Avast Firewall

Deep Inspection of Packets

Deep packet inspection is better than SPI because it can look at the contents of a packet in real time and dig deep enough to get information like the full text of an email. Routers with DPI can focus on traffic coming from or going to certain sites, and they can be set up to do certain things, like log or drop packets, when packets meet certain source or destination criteria. Routers with DPI can also be set up to look at certain kinds of data traffic, like VoIP or streaming media.