The files modified in the past day are listed using the find command in Linux.
find DIRECTORY -type f -mtime -1
The mtime parameter is the time of the file last modification, -1 is for the past 24 hours. The type f parameter is used to only test the files of the directory.
This example list all the files that have been modified in the current directory.
$ find . -type f -mtime -1 ./site/source/java/interview/how-to-reverse-a-LinkedList.txt ./site/source/linux/how-to-list-files-modified-in-past-day.properties ./site/source/linux/how-to-list-files-modified-in-past-day.txt
Note: This command can be used to on the directory / to investigate all the processes running and which one has modified the configuration of the computer. Passing a different parameter can returns files that have been modified earlier, in the past week or past month for example.