How do I permanently disable Pingbacks?

How can I permanently disable pingbacks on my wordpress multi user installation?

I have disabled access to the wp-trackback.php file through permissions (chmod 000 trackback.php) thinking this would stop any pingbacks from being received.

I do not want to run any SQL queries on the posts table, as there is a separate posts table for each blog.

Put this in a network activated plugin.

add_filter('pings_open','__return_false');

No more incoming pings.