A file catalog is a new feature with Windows PowerShell 5.1. A file catalog is a reasonably lightweight form of File Integrity Monitoring (FIM). The file catalog generates and stores SHA1 hashes for each file within a folder structure and writes the result to a catalog file.
About hashing
Hashing is a one-way process; a hash is not an encryption or encoding. A hash algorithm converts data of any length to a fixed-length value. The length of the value depends on the hashing algorithm used.
MD5 hashing is one of the more common algorithms; it produces a 128-bit hash that can be represented by a 32-character string.
SHA1 is rapidly becoming the default; it produces a 160-bit hash that can be represented by a 40-character string.
PowerShell has a Get-FileHash command that can be used to calculate the hash for a file.
Hashing is a one-way process; a hash is not an encryption or encoding. A hash algorithm converts data of any length to a fixed-length value. The length of the value depends on the hashing algorithm used.
MD5 hashing is one of the more common algorithms; it produces a 128-bit hash that can be represented by a 32-character string.
SHA1 is rapidly becoming the default; it produces a 160-bit hash that can be represented by a 40-character string.
PowerShell has a Get-FileHash command that can be used to calculate the hash for a file.
As the catalog is the basis for determining integrity, it should be maintained in a secure location, away from the set of files being analyzed.