Filtering in cyber security.
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What is Filtering in Cyber Security?

In this tutorial, you will learn what is filtering in cyber security, its types, how it works, and more.


Filtering is one of many cyber security defenses that organizations can implement as part of their threat management program. It’s a method for identifying and monitoring network traffic based on specific criteria, such as protocol, source address, or destination address. Not all traffic is malicious or dangerous; some is expected, necessary, and even desired.

Unfortunately, some network traffic poses a risk to your organization’s sensitive data and the devices themselves. Attackers might use a variety of methods to exploit this traffic to gain access to assets or users they shouldn’t have access to.

Filtering allows you to block unwanted connections and unauthorized users from the network while permitting only authorized connections from known sources. In this blog post, we’ll explain what filtering in cyber security means and why it’s so important for your organization.

Filtering in the Context of Cyber Security

The term filtering is used in many different contexts, but in the context of cyber security, it refers to the act of identifying and blocking malicious traffic. Identifying and blocking malicious traffic is particularly important in the commercial sector, as organizations need to protect their assets, sensitive data, intellectual property, and customers’ personal information.

A business’s customers are not the only people who benefit from filtering; the employees also rely on it to keep their computers and other devices safe from malicious attacks. Network traffic is the exchange of data between connected devices on a network. Traffic may include applications such as email, web browsing, or file transfers, as well as data related to those applications, such as email addresses and IP addresses.

Why is Filtering Important?

Filtering is one of the most fundamental cybersecurity practices, as it allows you to control and manage network traffic. It’s critical for organizations to be able to define what is and isn’t allowed on their networks.

There are many factors that can influence which filtering strategy a business decides to implement, including its industry sector, regulatory compliance requirements, and organizational risk tolerance. The main goal of filtering is to maintain control of the network, allowing only acceptable traffic and blocking all others.

This means the organization can protect itself and its assets by controlling which devices are permitted to connect to the network and what kind of information they are allowed to send or receive. Filtering also allows organizations to identify and prevent suspicious traffic, including malicious software and attacks, such as denial-of-service or man-in-the-middle attacks.

Types of Filtering in Cyber Security

The following are the types of filtering in cyber security:

  1. ACLs - An ACL is a rule that determines what network traffic is permitted or denied at the network layer. ACLs are used in routing protocols and firewalls to filter traffic.
  2. Blacklists and Whitelists - Blacklists and whitelists are databases of IP addresses, URLs, or other information that is used to identify and block or permit traffic. For example, a blacklist might contain IP addresses of computers that have attempted network attacks, while a whitelist would include IP addresses of trusted computers.
  3. Deep Packet Inspection - While all filtering techniques examine network traffic, deep packet inspection goes a step further, analyzing the packets themselves to determine their content.
  4. Port Filtering - Port filtering examines both network traffic and the content of packets to restrict certain ports, as well as the types of devices permitted to connect via those ports.
  5. Source and Destination Addresses - Source and destination address filtering examines the source and destination addresses of network traffic to determine whether it is permitted or blocked.

Limiting and Scoping Traffic with ACLs

An access control list (ACL) is a rule that identifies permission and restriction settings for network traffic. These rules are applied to network devices, such as routers, switches, and firewalls, and they control the flow of traffic between devices.

ACLs can be used to limit and scope network traffic by blocking or permitting certain sources or destinations. For example, if a device is attempting to send data to an unsecured website but it’s not permitted to do so, an ACL can be applied to block that connection. ACLs can also be used to limit the amount of network traffic between a particular source and destination address.

Limiting Network Traffic with Firewalls

Firewalls are one of the most common ways to filter network traffic. Firewalls are devices that examine both network traffic and the content of packets to determine whether they should be permitted or blocked. Firewalls can be implemented at the network edge, the Internet edge, or both, depending on the network architecture.

They can also be used to filter traffic between internal networks. The first step in filtering network traffic in cyber security with a firewall is to identify the traffic you want to permit. Once you’ve done that, you can use rules to identify the traffic you want to block. Firewall rules are applied inbound or outbound and can be based on specific criteria, such as protocol, source address, or destination address.

Final Words on Filtering in Cyber Security

A cyber attack can be catastrophic for any organization, so it’s important to implement cyber security defenses. Filtering in the context of cyber security is an important practice that helps you manage network traffic and prevent malicious connections, attacks, and data theft. There are many types of filtering that organizations can implement to control network traffic, including ACLs, blacklists and whitelists, deep packet inspection, port filtering, and source and destination address filtering.

Written by Lancy Joseph

A hardware and software engineer, having more than 20 years of experience in the IT industry. Likes to write to share the solutions with the people.

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