What is that .fdb file?

On Unix the Nanitor Agent stores a .fdb /var/lib/nanitor/agent/. FDB stands for a file database, and this is where Nanitor stores a list of all files on the system (excluding /proc, /dev, nfs, smb, and other similar resources). The reason for storing this is the CIS benchmarks require checking files recursively and instead of scanning them every time we keep a .fdb that creates and maintains that database in an efficient manner. This can become a few gigabytes if the filesystem has an enormous number of files.