Comparing file hashes of files that you have downloaded to your computer with those provided by the provider of said downloads can be a great way of verifying that a file is genuine and that it has not been tampered with by third parties.
Security only works if the sources you get the files and hashes from are trustworthy. If an attacker tampered with a file and the hash displayed on the download site the download would verify as legitimate even though it would not be.
One example of how this can help would be if you uploaded a file on a server to download it later to another computer.
You'd generate the hash, upload the file and verify that the hash is identical to the one that you have generated before. This can also be useful for backups to make sure they are not corrupt.
MD5 Reborned Hasher is a Firefox add-on that integrates md5 hash generating options directly in the browser's download window. Having said that, it needs to be noted that users need to keep a history of their downloads in the browser for the add-on to work properly.
The add-on places a small Check Digest link next to each download in the Downloads window of the browser. A click on the link opens a Check File window where hash files can be generated. The add-on supports the generation of MD2, MD5, SHA1, SHA256, SHA384 or SHA512 hashes. Just select the desired hash from the pulldown menu and click the Generate Digest button afterwards.
The generated checksum is then displayed in the same window. All that is left then is to copy the original hash value into the second field. The add-on compares both hashes and will notify you if they are identical or not.
Depending on the result you may either decided to quarantine or delete the file or use it on your system.
MD5 Reborned Hasher is a handy extension for Firefox users who need to verify file downloads regularly. An option to automatically generate hashes for all downloaded files would be handy but is not present in the reviewed version of the add-on.
Firefox users can download and install the extension from the official Mozilla Firefox add-on repository.
Update: The Firefox add-on is not compatible with versions 26 and up of the web browser. This has likely something to do with the download interface change that Mozilla introduced last year.
Windows users can try a free alternative such as Checksum Compare instead.
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Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.