File Integrity Monitoring (FIM)
File Integrity Monitoring (FIM) is a security process and technology that helps organizations monitor and detect file changes, ensuring the integrity of their operating system and application software files. FIM systems establish a baseline of a system’s files in a known good state, including critical attributes of the files at that time. Any subsequent changes to these files are reported through real-time alerts, which can indicate potential security breaches such as malware infection or unauthorized modifications by insiders. The process is critical in compliance with various regulatory frameworks requiring sensitive data and systems monitoring. FIM tools often provide detailed information about when a file was changed, who changed it, and what exactly was changed, allowing security teams to assess and respond to potential threats quickly.
Architecture Diagram for File Integrity Monitoring (FIM)
File Integrity Monitoring is an area where organizations can leverage open-source tools for better security. Some of the popular open-source FIM tools include:
1. OSSEC: OSSEC, short for Open Source Security, is one of the most well-known Host-based Intrusion Detection System (HIDS) that has FIM functionality. OSSEC checks file integrity and log files, among other attributes such as registry, and then sends alerts in case of unauthorized changes. Moreover, OSSEC is a multi-platform agent with powerful alerting and reporting capability.
2. Tripwire Open Source: The developer also offers a free version of its FIM software in the form of Tripwire Open Source. This standalone utilizes FIM to monitor files and directories on the system, alerts in case of change, and supports reporting and policy management. However, this solution is less scalable and doesn’t support external databases.
3. AIDE: Another open-source FIM tool designed for Unix-like systems is AIDE, which stands for Advanced Intrusion Detection Environment. It creates file hashes and compares them against the database periodically to track changes. AIDE is fair for a small environment because it may be cumbersome in terms of the number of alerts.
4. Samhain: Samhain is a host-based intrusion detection system with FIM functionality and goes beyond that. It supports file changes in a real-time or periodic manner and supports centralized logging and anomaly detection.
5. Integrit: Integrit is another simple and open-source FIM tool for Unix-like systems. It compares the file hashes against the baseline periodically or on-demand, which is very simple in configuration;
6. Open Source Tripwire: Like other commercial vendors, Tripwire offers an open-source software version. Open-source Tripwire is another option to consider, but the community contribution can sometimes be lacking, so it’s better to use the previous option.
