local nPullevent = os.pullEvent -- So you cant terminate the program
os.pullEvent = os.pullEventRaw

while true do
    term.clear()
    term.setCursorPos( 1,1 )

    print( "Keltecfanboy Security System V2.0" )
    print( "Right click on the ..." )

    rednet.open( "back" )

    local file = fs.open( "ulist", "r" )
    local reader = file.readAll()
    file.close() -- you ALWAYS should do that.

    local players = textutils.unserialize( reader ) -- You have to serialize before you write to a file

    local evt, player = os.pullEvent( "player" )
    local succes = false
    for i = 1, #players do
        if player == players[i] then
            rs.setOutput( "bottom", true )
            sleep( 8 )
            rs.setOutput( "bottom", false )
            succes = true
            break
        end
    end

    if not succes then
        print( "Unauthorized user!" )
        rednet.send( 2, "attack" ) -- we can send only strings OR variables wich are strings
    else
        break
    end
end

os.pullEvent = nPullevent