FIM

FIM is a free, open-source file monitoring tool for teams that can deploy software on the endpoints they manage. It combines change events with file history and integrity checks, with particularly useful attribution on Linux.

Overview

FIM runs in the background, records historical file data, and emits an event when a monitored file changes. It detects changes to content, attributes, ownership, and permissions, while automatically generating hashes and analyzing changes. This gives administrators more to work with than a simple changed-or-unchanged signal.

On Linux, using the Linux Audit daemon, FIM can identify who caused an event and which command produced it. That context can help narrow an investigation; it is a Linux-specific strength, not a reason to expect the same attribution across every supported operating system. Events can be written locally, sent over the network, or sent to both destinations.

Key features

• File-change events and history: Background monitoring and retained historical data support ongoing integrity review. Storage use increases over time, so the small stated minimum does not remove the need to plan for growth.
• Integrity checks: Automatic hashes and change analysis help identify changes to monitored files.
• Change detail: Content, attributes, ownership, and permissions are all in scope, which makes FIM relevant when configuration or access-control changes matter as much as edits.
• Event routing: Local-file and network destinations can be used separately or together. Documented integrations include Elasticsearch 8.x or OpenSearch 2.x and Splunk indexer 9.x, but only one integration can be active at a time. That is a meaningful constraint for teams that need to route to multiple listed platforms simultaneously.
• Endpoint deployment: FIM is on-premises and not agentless. Minimum requirements are 1 CPU core, 128 MB memory, and 1 GB storage; storage usage grows with time.

Pricing

FIM costs nothing as free, open-source software. There is no trial to consider because the software is free, and no usage limits are stated. Achiefs says support is free and invites users to contact [email protected].

The free plan is the only plan described, so there is no paid tier with additional capacity or features to weigh against it. Its trade-off is operational rather than a stated usage cap: teams must handle on-premises deployment and account for growing storage use. Linux, macOS, and Windows support makes the no-fee option relevant across mixed desktop environments.

Platforms

FIM supports Linux, macOS, and Windows. The installation guide names Ubuntu Xenial or later, CentOS 7 or later, Windows 7 or Windows Server 2016 or later, and macOS Big Sur or later. Those minimum versions help establish whether an existing fleet fits, while the one-integration-at-a-time limit remains relevant regardless of platform.

Who it's for

FIM is a sensible fit for organizations seeking no-fee file-integrity monitoring on endpoints they can manage directly, especially where Linux event attribution is valuable. It is less suitable for teams that need agentless monitoring, multiple active integrations, or a deployment model other than on-premises.

Pros and cons

• Pro: Hashing, change analysis, and historical data make the event stream useful for ongoing integrity tracking.
• Pro: Linux Audit daemon support can identify the user and command behind a change, adding investigative context.
• Pro: Free, open-source software is available for Linux, macOS, and Windows.
• Con: Only one listed integration can be active at once, limiting simultaneous routing to the documented Elasticsearch/OpenSearch and Splunk options.
• Con: On-premises deployment is not agentless, so teams need to install and maintain software on monitored systems.
• Con: Storage consumption grows over time, requiring capacity planning even with a 1 GB minimum.

Alternatives

For broader network monitoring alongside file-integrity work, Paessler PRTG Network Monitor has a free tier capped at 100 sensors, about 10 devices, as well as paid plans and a free trial; its platform list is broader, including mobile and web. EventSentry File Monitoring is worth comparing if monitoring five machines with basic log monitoring and community support is enough: its free Light plan excludes SIEM capability and dashboards, while a trial is available.

Wazuh is another free, open-source self-hosted option, with a paid Small plan starting at $571 a month and a free trial. Open Source Tripwire is a free GPL-2.0 file and directory integrity-monitoring alternative. OSSEC offers a free command-line plan with core rules and no dedicated support staff, plus a free trial. OWASP Amass is a free Apache License 2.0 open-source framework. AIDE is a free GPL-2.0 licensed option for Linux, macOS, and self-hosted environments. Elastic Security is a freemium alternative with a free plan and trial, and its platform list includes API, Linux, self-hosted, and web.

See more options in File Integrity Monitoring Software.

Verdict

Choose FIM if you want free, cross-platform file monitoring with history, integrity checks, and useful Linux event attribution, and can operate it on premises. Look elsewhere if agentless monitoring or simultaneous integrations are essential; those are the clearest constraints on fitting it into a broader monitoring setup.