Linux Intrusion Detection and Response (IDS), Linux Endpoint Detection and Response (EDR) and Cloud Detection and Response (CDR) are different security techniques for the analysis and identification of unusual behavior patterns or actions in a system.

These may have a common objective, but they are still quite different:

• Linux IDS is focused on systems with Linux as operating system to detect unwanted access in these.
• Linux EDR on the other hand, also intended for systems with Linux as the operating system, searches for possible threats in the system endpoints by monitoring and detecting suspicious behavior.
• CDR is defined in the field of the cloud, in charge of searching and detecting all types of threats and minimizing them to reduce the impact that the system may suffer.

This article breaks the differences between Linux IDS and Cloud Detection and Response and what they mean and how they compare. We’ll also look at where related practices, such as Linux Endpoint Detection and Response, fit in.

Detection and Response security

At a high level, Linux IDS and CDR both fall under the umbrella of detection and response security.

Detection and response security is a discipline within cybersecurity that focuses on detecting and reacting to threats. Typically, detection and response security works by monitoring various types of data sources (such as log files and operating system metrics) for signs of a breach or attempted breach, determining the nature of the risk, and then reacting accordingly.

Detection and response security isn’t the only type of operation that powers an overall cybersecurity strategy. Businesses also usually need resources like threat intelligence and security posture management to reduce their overall risk of attack. But as the means by which active threats or risks are detected and mitigated, detection and response is one of the foundational elements of modern cybersecurity.

What is IDS (Intrusion Detection and Response) for Linux?

One example of detection and response security is Intrusion Detection and Response for Linux.

IDS for Linux is the use of various data sources produced by a Linux environment – such as network connections, syslog (the generic Linux system events log), and auth.log (which records authentication activity on Linux) – to detect and respond to risks.

There are multiple ways to implement IDS for Linux; for example, you could use an agent-based approach in which you run software agents on each Linux system to monitor the environment, or you could deploy an agentless architecture that collects the necessary data over the network without requiring agents to run locally. Either way, however, the main goal of Linux IDS is to detect unusual activity, determine whether it is associated with a security risk, and then take effective action if it is.

As an example of IDS for Linux at work, consider a scenario where a series of new processes suddenly appear within a Linux system. If your IDS tools have been monitoring the system continuously, the new processes will stand out as an anomaly. That information on its own doesn’t necessarily mean a breach or attempted breach has occurred, but the IDS tools might correlate the event with other unusual activity – such as a high number of failed authentication attempts recorded in auth.log shortly before the processes appeared – to make an informed assessment about whether an intrusion has occurred on the system. If it has, the IDS software will notify security admins so they can respond.

What is CDR (Cloud Detection and Response)?

Cloud Detection and Response (CDR) is the use of data from a cloud environment to detect and respond to security threats.

The data sources that drive CDR can vary depending on which cloud platform you use to operate your workloads, as well as which specific types of cloud services the workloads rely on. For example, if you have a load balancer set up, you can typically track network access requests and patterns by studying its logs, but not all cloud environments include load balancers. Some cloud providers also offer auditing tools (like AWS CloudTrail or Cloudwatch) that record account activity, providing information similar in some respects to auth.log on Linux, but the exact nature of the auditing and authentication data they provide can vary.

That said, although your data sources may vary from one environment to another, all CDR tools share the common traits of analyzing various types of data in order to detect security threats that could impact a cloud environment.

Linux IDS vs. CDR

In many – though certainly not all – cases, the operating system that powers the servers that host cloud workloads is some form of Linux. For that reason, the types of data sources and analytics processes that power Linux IDS are the same in some cases as those behind Cloud Detection and Response.

For example, if you deploy cloud workloads on VM instances using a service like Amazon EC2, you could monitor the logs of the operating system installed on each VM as one source of data for detecting threats and risks. You could also monitor the processes running on each system.

That said, there are important differences between Linux IDS on traditional hosts and Cloud Detection and Response:

• Level of visibility: In a cloud environment, you may have VMs that run Linux, but you typically don’t have access to the underlying physical servers, even if they also run Linux. Only your cloud provider can view data from the underlying infrastructure and use it for security monitoring purposes. In an on-prem environment, you’d have complete access to security monitoring data at all layers of your stack.
• Virtual infrastructure: In cloud environments, Linux-based workloads often make use of virtual infrastructure, which results in different types of monitoring data for IDS purposes. For example, if you want to monitor network traffic for Amazon EC2 instances, you’d generally have to configure an Elastic Network Adapter (ENA), a type of virtual network interface, and monitor traffic through it. With an on-prem Linux host, you could monitor traffic using physical network interfaces.
• Centralized cloud logging: Most cloud environments include centralized logging tools – like CloudWatch and CloudTrail – that collect data from across multiple hosts or other resources. As a result, it’s easier with CDR to analyze data using centralized sources. With individual Linux hosts, data is usually not aggregated by default (although you can set up an aggregation solution, such as a centralized syslog server, if you wish).
• Different types of services: With some cloud services, there are no servers that users can access at all. For example, if you use serverless functions in the cloud, you have no ability to collect logs or metrics from the host operating system. The data you use for CDR purposes is therefore limited to whichever metrics and logs your cloud provider exposes for your serverless functions.

The bottom line: even if your cloud environment is based on Linux, the data sources and analytics processes you use to detect security risks in the cloud are likely to look quite different from those that apply in an on-prem Linux environment.

What about Endpoint Detection and Response?

A discipline that is closely related to Linux IDS is Endpoint Detection and Response, or EDR. EDR is the use of security analytics to protect endpoints, meaning any physical or virtual device connected to the network.

Since endpoints may include (but are not limited to) Linux-based devices, the practices behind Linux IDS are similar in some cases to those of EDR. In other words, EDR for a Linux server is likely to rely on analyzing the same data sources and looking for the same types of threats as IDS for a Linux server.

That said, there are some important differences between Linux EDR and Linux IDS:

• IDS focuses primarily on detecting active intrusions, whereas EDR is a broader discipline that also includes hardening endpoints in order to reduce the risk of attack.
• EDR can extend to any type of endpoint – such as mobile devices, PCs, and even printers – whereas IDS is used more frequently on traditional types of hosts, like servers.
• By some definitions, IDS focuses on detecting threats by analyzing network activity, whereas EDR uses other data sources (like logs and metrics). That said, this interpretation is somewhat subjective; there is no law that says you can’t use non-network related data sources for EDR purposes or that network data alone can be used for IDS.

Similar differences help to distinguish Linux EDR from CDR. With EDR, you’re focusing on securing individual Linux hosts, whereas CDR is a broader practice that extends to any type of resource in the cloud, not just physical and virtual Linux servers.

Conclusion

Linux IDS, EDR, and CDR all play an important role in protecting modern environments. But each type of solution works in a different way and serves a different purpose, which is why most organizations need all three types of security monitoring and defense solutions to detect and respond to threats effectively.