This article covers how to install AIDE on Ubuntu 20.04. In fact, AIDE is an intrusion detection system that detects changes to files on the local system. It creates a database from the regular expression rules that it finds from the config file. Once this database is initialized it can be used to verify the integrity of the files. It has several message digest algorithms (md5, sha1, rmd160, tiger, haval, etc.) that are used to check the integrity of the file.