This is a quick and easy bit of command line to check the integrity of your files. Many downloads can come with a md5 checksum file or you can create your own for your own files.

 After running the compare command you will see if the files have been altered, be it by you or outside nefarious forces.

Create md5 file:

md5sum > checksum.md5

Compare md5 file against files :

md5sum -c checksum.md5