.fsa is a file extension used for raw fragment analysis data, often in forensic or human-identification workflows. It typically stores signal information generated by an instrument before the data is interpreted by analysis software. In other words, it is an input file, not a final report.
From a security perspective, .fsa files matter because any change made before import can affect the result while still looking valid to an analyst. Attackers or careless insiders could tamper with the file on shared drives, transfer paths, or staging folders to alter downstream interpretation. Defenders protect these files with strict access controls, hash verification, audit logging, and chain-of-custody procedures so the sample remains trustworthy from collection to analysis.