Warning about copying information

Increasingly, there was a warning about copying information on media sites and a request to put a link. Maybe this is an ancient way to the world, but I have never seen it on sites more serious than my homepage.
Maybe someone will come in handy ...

<script type= "text/javascript" >
function rightsf() {
alert( " . \n - ." );
}
oncopy= 'rightsf();'
</script>


and
')

< body oncopy ="rightsf();" >


It will be very interesting to learn other ways and ideas to prevent and protect texts from copying.