Something

<?php
$ban = "bans/" . $_SERVER["REMOTE_ADDR"];

if (file_exists($ban)) {
	if (filemtime($ban) > time() - 3600) {
		if (intval(file_get_contents($ban)) >= 3) {
			header("HTTP/1.1 403 Forbidden");
			die("403 Forbidden");
		}
	}
	else
		@unlink($ban);
}

function login_failed() {
	global $ban;
	if (file_exists($ban)) {
		$count = intval(file_get_contents($ban));
		file_put_contents($ban, ++$count);
	}
	else
		file_put_contents($ban, 1);
	return;	
}

?>