I installed the plugin from https://downloads.www.ads-software.com/plugin/swift-security-lite.zip
Then click on Activate plugin and the below msg. This only happens with your plugin as the right installed ok.
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator at root@localhost to inform them of the time this error occurred, and the actions you performed just before this error.
More information about this error may be available in the server error log.