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TechKnowSurge Catalog Videos File Integrity Monitoring (FIM)
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File Integrity Monitoring (FIM)

File integrity monitoring (FIM) detects unauthorized changes to critical system files, helping security teams identify compromised servers before damage spreads. It is a core capability in modern SIEM deployments.

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About this video

Attackers who gain access to a server often move quickly to modify files — replacing application code, altering configuration settings, or injecting malicious scripts that execute whenever legitimate users connect. In a software-as-a-service environment, this kind of tampering can turn a trusted application server into a delivery mechanism for malware, affecting every user who accesses it. Detecting these changes quickly is critical to limiting the blast radius of a compromise, and that is the core purpose of file integrity monitoring (FIM). FIM works by establishing a known-good baseline for critical files and then continuously comparing the current state of those files against that baseline. A central FIM server coordinates monitoring across the environment, with lightweight agents installed on individual machines to watch for unauthorized additions, deletions, or modifications. When a change is detected, the system flags it so security personnel can investigate whether the change was part of a legitimate update or a sign of active intrusion. FIM is widely integrated into SIEM platforms, where file change events are collected alongside other log data to provide broader context. This correlation capability allows analysts to connect a suspicious file modification to related network activity or authentication events, making it a valuable component of a mature security monitoring strategy.

What you'll learn

What's covered

File Integrity Monitoring

Aligned to

NIST 800-53
SI-7 Software, Firmware, and Information Integrity
SI-4 System Monitoring
NIST CSF
DE.CM-09 Computing hardware and software, runtime environments, and their data are monitored to find potentially adverse events.
DE.AE-03 Information is correlated from multiple sources.
CompTIA Security+
4.4 Explain security alerting and monitoring concepts and tools.
ISC2 CISSP
7.7 Operate and maintain detection and preventative measures
7.2 Conduct logging and monitoring activities
CompTIA CySA+
1.3 Given a scenario, use appropriate tools or techniques to determine malicious activity.

Key terms

File Integrity Management
FIM
File Integrity Management monitors critical system files and configurations for unauthorized changes by comparing current state against a trusted baseline, detecting tampering or malware activity.
Security Information and Event Management
SIEM
A system that aggregates and analyzes security event data from across an organization to detect and respond to threats.
Baseline
A documented set of minimum security standards or performance metrics used as a reference point.
Integrity
The assurance that data has not been tampered with and remains accurate and complete.
Incident Response
IR
A structured process for identifying, containing, eradicating, and recovering from security incidents.
Log Management
The process of collecting, storing, analyzing, and monitoring log data generated by systems and applications.

Topics

File Integrity Monitoring Siem Threat Detection Incident Response Cybersecurity Log Management

Transcript

Why Files Get Altered

One of the things that attackers may do is try to start altering files. What I mean by that is, let's say you have a web application that's up and running and somebody's compromising that web application. They would be going in there and changing some of the code, which is on files, or some of the settings, which is on files. So when those files start changing, it's a sign that there's a compromise on the system.

One of the things that we're going to want to monitor is the files on the system, and that's why we would implement something like a file integrity monitoring system.

A Scenario

Let's create a little scenario here. Let's say we have a SaaS company — it's a software as a service company — and so we have an application that's being hosted and people are accessing this application server.

Now let's say we're under attack and somebody compromised the server. One thing that they may do is start replacing some of the files, so that way when users are accessing this server right here they're actually accessing malicious code and getting malicious code. This is obviously problematic.

So one thing we want to monitor is the files of systems, and so we're going to do file integrity monitoring to make sure that we understand what's changing, how it's changing, and why it's changing.

Rolling It Out

One thing that we may do is set up a server to have this file integrity monitoring software on it, and what it would do is then we would install maybe clients on all of the machines out there, and then it would monitor to see if the critical files ever get changed and then flag those files, so we can go in and find out what's going on.

This is one of the common features as part of a SIEM. So you have a SIEM that you roll out, and maybe you are collecting this file integrity monitoring logs and system information, so you can understand when things are changing on your network.

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