WordPress at a glance
filter is not described

login_message filter-hook . WP 2.1.0

Filters the message to display above the login form.

Usage

add_filter( 'login_message', 'filter_function_name_7271' );
function filter_function_name_7271( $message ){
	// filter...

	return $message;
}
$message(string)
Login message text.

Where the hook is called

login_header()
wp-login.php 197
$message = apply_filters( 'login_message', $message );

Where the hook is used (in WP core)

Does not used.