Disable WordPress Updates

functions.php

add_filter( 'pre_site_transient_update_core', create_function( '$a', "return null;" ) );

# Disable WP>3.0 plugin updates
remove_action( 'load-update-core.php', 'wp_update_plugins' );
add_filter( 'pre_site_transient_update_plugins', create_function( '$a', "return null;" ) );

# Disable WP>3.0 theme updates
remove_action( 'load-update-core.php', 'wp_update_themes' );
add_filter( 'pre_site_transient_update_themes', create_function( '$a', "return null;" ) );

# disable core updates:
add_filter( 'pre_site_transient_update_core', create_function( '$a', "return null;" ) );