addEventHandler(\"onElementDataChange\", root,
    function(dataName, oldValue)
        -- Check data is coming from a client
        if client then
            -- Validate \'special_thing\'
            if dataName == \"special_thing\" then
                -- \'special_thing\' can only be set by a client on its own player
                if client ~= source then
                    -- Illegal activity here, so log and revert the change
                    reportAndRevertDataChange( dataName, oldValue, source, client )
                end
            end
            -- Validate \'flag_waving\'
            if dataName == \"flag_waving\" then
                -- \'flag_waving\' can only be set by a client on its own vehicle
                local vehicle = getPedOccupiedVehicle(client)
                if vehicle ~= source then
                    -- Illegal activity here, so log and revert the change
                    reportAndRevertDataChange( dataName, oldValue, source, client )
                end
            end
        end
    end
)
-- Helper function to log and revert changes
function reportAndRevertDataChange( dataName, oldValue, source, client )
    -- Report
    outputConsole( \"Possible rouge client!\"
            .. \" client:\" .. tostring(getPlayerName(client))
            .. \" dataName:\" .. tostring(dataName)
            .. \" oldValue:\" .. tostring(oldValue)
            .. \" newValue:\" .. tostring(getElementData(source,dataName))
            .. \" source:\" .. tostring(source)
            )
    -- Revert (Note this will cause an onElementDataChange event, but \'client\' will be nil)
    setElementData( source, dataName, oldValue )               
end