My Moodle was working fine on Monday evening close of business and on Tuesday morning it was down with the following error 500 Internal Server Error.
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, email@example.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
I have spoken to the hosting company and they stated that its an issue with the .htaccess file within the Moodle directory.
This is caused by invalid entries in the .htaccess file from within the main folder of (Moodle address on webserver), which seem to have been made intentionally. For more info regarding this, please see the following thread from Moodle's bug tracker: https://tracker.moodle.org/browse/MDL-16957
I have looked at the bug tracker but it's in relation to version 1.7 where as I am running version 2.6 (Build: 20131118).
Any advice or guidance would be much appreciated.