What is File Integrity Monitoring and Why Do I Need It?

File integrity monitoring (FIM) is an internal control that examines files to see the way that they change, establishing the source, details and reasons behind the modifications made and alerting security if the changes are unauthorized. It is an essential component of a healthy security posture. File integrity monitoring is also a requirement for compliance, including for PCI-DSS and HIPAA, and it is one of the foremost tools used for breach and malware detection. Networks and configurations are becoming increasingly complex, and file integrity monitoring provides an increased level of confidence that no unauthorized changes are slipping through the cracks.

How Does File Integrity Monitoring Work?

In a dynamic, agile environment, you can expect continuous changes to files and configuration. The trick is to separate between authorized changes due to security, communication, or patch management, and problems like configuration errors or malicious intent that need your immediate attention.

File integrity monitoring uses the process of baseline comparison to make this differentiation. One or more file attributes are stored internally as a baseline, and this is then compared periodically when the file is being checked. Examples of baseline data used could be user credentials, access rights, creation dates, or last known modification dates. In order to ensure the data is not tampered with, the best solutions calculate a known cryptographic checksum, and can then use this against the current state of the file at a later date.

File Integrity Monitoring: Essential for Breach Detection and Prevention

File integrity monitoring is a prerequisite for many compliance regulations. PCI DSS for example mentions this foundational control in two sections of its policy, For GDPR, this kind of monitoring can support five separate articles on the checklist. From HIPAA for health organizations, to NERC-CIP for utility providers, file integrity monitoring is explicitly mentioned to support best practice in preventing unauthorized access or changes to data and files.

Outside of regulatory assessment, although file integrity monitoring can alert you to configuration problems like storage errors or software bugs, it’s most widely used as a powerful tool against malware.

There are two main ways that file integrity monitoring makes a difference, Firstly, once attackers have gained entry to your network, they often make changes to file contents to avoid being detected. By utilizing in-depth detection of every change happening on your network and contextually supporting alerts based on unauthorized policy violations, file integrity monitoring ensures attackers are stopped in their tracks.
Secondly, the monitoring tools give you the visibility to see exactly what changes have been made, by whom, and when. This is the quickest way to detect and limit a breach in real-time, getting the information in front of the right personnel through alerts and notifications before any lateral moves can be made or a full-blown attack is launched.

Incorporating file integrity monitoring as part of a strong security solution can give you even more benefits. Micro-segmentation is an essential tool that goes hand in hand for example. File integrity monitoring can give you the valuable information you need about where the attack is coming from, while micro-segmentation allows you to reduce the attack surface within your data centers altogether, so that even if a breach occurs, no lateral movement is possible. You can create your own strict access and communication policies, making it easier to use your file integrity monitoring policies to see the changes that are authorized and those which are not. As micro-segmentation works in hybrid environments, ‘file’ monitoring becomes the monitoring of your entire infrastructure. This extended perimeter protection can cover anything from servers, workstations and network devices, to VMware, containers, routers and switches, directories, IoT devices and more.

Features to Look for in a File Integrity Monitoring Solution

Of course, file integrity monitoring can vary between security providers. Your choice needs to be integrated as part of a full-service platform that can help to mitigate the breach when it’s detected, rather than just hand-off the responsibility to another security product down the line.

Making sure you find that ideal security solution involves checking the features on offer. There are some must-haves, which include real-time information so you always have an accurate view of your IT environment, and multi-platform availability. Most IT environments now use varied platforms including different Windows and Linux blends.

Another area to consider is how the process of file integrity monitoring seamlessly integrates with other areas of your security posture. One example would be making sure you can compare your change data with other event and log data for easy reporting, allowing you to quickly identify causes and correlative information.

If you’re using a micro-segmentation approach, creating rules is something you’re used to already. You want to look for a file integrity monitoring solution that makes applying rules and configuring them as simple as possible. Preferably, you would have a template that allows you to define the files and services that you want monitored, and which assets or asset labels contain those files. You can then configure how often you want these monitored, and be alerted of incidents as they occur, in real-time.

Lastly, the alerts and notifications themselves will differ between solutions. Your ideal solution is one that provides high level reporting of all the changes throughout the network, and then allows you to drill down for more granular information for each file change, as well as sending information to your email or SIEM (security information and event management) for immediate action.

File Integrity Monitoring with Micro-Segmentation – A Breach Detection Must Have

It’s clear that file integrity monitoring is essential for breach detection, giving you the granular, real-time information on every change to your files, including the who, what, where and when. Alongside a powerful micro-segmentation strategy, you can detect breaches faster, limit the attack area ahead of time, and extend your perimeter to safeguard hybrid and multi-platform environments, giving you the tools to stay one step ahead at all times.

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