Most of the times when you download a file from internet, you will see a checksum or MD5 hash tag beside the download link so you can compare the checksum of the downloaded file with the original file. There are several security reasons for that, but the most common one is to eliminate the possibility of a special type of hacking called “Man in the middle”. In this type of hacking, the hacker usually sniffs and listens to the requests goes from your computer and tries to compromise the packets, but the best thing you can do to help the hacker is to request a very popular application that he has already prepared an infected version, so when you want to download the file, he will send his own infected version toward your computer and you will install that application, thinking that it is the original malware-free application !! so after installing the application, the hacker can do variety of dangerous things to your computer such as creating a backdoor, key-logging, screen capturing, infecting the entire trusted network and etc.
The only way you can avoid this type of hack is by checking the checksums. there are few awesome, useful and easy commands that can do this checking for you and I’m going to describe them in this article: