What is CHMOD and how does it affect security? - Powered By Kayako SupportSuite

08 Sep 2010

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	What is CHMOD and how does it affect security?

Solution CHMOD is used to set file and folder permissions in UNIX/Linux based systems. For example, allowing a folder to be world-writeable (e.g. chmod 777) might allow someone with bad intentions to modify your website's files. If in doubt, it is always a safe bet to chmod any file or directory 755.

Certain FTP clients such as Cute FTP and WS/FTP Pro allow for a chmoding directly within FTP. To do this you would highlight the file that you want to use, and select from the command menu "change file permissions." There is on option for "manual." This is where you will enter the desired CHMOD. Many other FTP clients will support CHMODing as well, we recommend checking the documentation.

Other Reasons for CHMODING

CHMODing files can be done for a variety of reasons. You can CHMOD files to do things such as: mark them executable, give them write permission, restrict access to them, and a variety of other reasons. It is important to note that chmoding is nearly impossible to avoid. If you are trying to run a certain cgi script it could require execute permissions on the script itself, write permissions on a directory, and read on an informational page. Your cgi scripts should contain the proper documentation to inform you of the proper CHMOD's.

List of some common CHMOD's and what they mean

chmod 777 filename - The file is available for Read, Write, and Execute for the owner, group, and world.

chmod 755 filename - The file is available for Read, Write, and Execute for the owner; and Read and Execute only for the group and world.

chmod 644 filename - The file is available for Read and Write for the owner, and Read only for the group and world.

chmod 666 filename - The file is available for Read and Write for the owner, group, and world. I wonder if the 666 number is just a coincidence. Anybody can create havoc with your files with this wide-open permission mask.

Additional technical information can be found at:

http://catcode.com/teachmod/
http://support.discusware.com/center/resources/howto/chmod.html

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Created On:

06 Jun 2007 09:51 PM