File Checksum Integrity Verifier is a free command line program by Microsoft that can be used to create and verify md5 checksums of files in a specific folder.
The program can for instance be used to check if files in a specific directory have been modified, which is often the case if malicious software has been executed on the computer system.
This is done by calculating hashes of every file - or only specific file types - in the selected directory with the option to compare those generated the first time with hashes that have been generated at a later time.
Identical hashes mean no file manipulation while nonidentical hashes suggest file manipulations. This does not necessarily mean an attack as updates may replace files as well and change their checksum in the process.
The File Checksum Integrity Verifier can be downloaded from the Microsoft homepage. The Microsoft Support page that lists the file download contains an explanation of the program's command line parameters.
The program needs to be unpacked after download. It is suggested to move the file fciv.exe into a system folder like the Windows folder so that it can be run without specifying a path but that is up to you.
MD5 hashes of a specific directory can be created with the following command:
fciv folder -r -xml output.xml
fciv c:\windows\ -r -xml c:\md5\20100117md5.xml
It is possible to specify file extensions with the -type parameter followed by the filetype, e.g. *.exe.
A previously created xml document containing hashes can be verified with the following command
fciv -v -xml output.xml
fciv -v -xml c:\md5\20100117md5.xml
The tool will display a list of modified files at the end of the comparison. It is possible to switch to use -sha instead of -md5. Users who want to verify the files regularly might want to consider creating a batch file for the file verification checks.
The tool can be very useful if you want to make sure that important files -- say files on a web server, documents, or program files -- have not been tampered with.
Update: Microsoft has removed the program from its servers, it is no longer available. You can check out the third party alternatives File Check MD5 or File Verifier++ which offer a similar feature set.
Update 2: And the tool is up again. You can download it from Microsoft with a click on the link in the summary below.
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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.