root@rowla:~# ps auxw | grep katester | grep perl
katester     23802 94.4  0.1  3184  2520  ??  R    Wed01PM 1582:07.71 perl udp.pl irc.world-crew.net 6667 1200 (perl5.8.8)
root@rowla:~# kill 23802

http://www.whoopis.com/howtos/phpbb-viewtopic-hack/udp.txt

root@rowla:~katester# ps -U katester
  PID  TT  STAT      TIME COMMAND
17603  ??  Z      0:00.01 <defunct>
17605  ??  S      0:03.76 ./bash
23800  ??  Z      0:00.00 <defunct>
51838  ??  I      7:27.67 /usr/local/bin/php-cgi
51842  ??  I      7:17.46 /usr/local/bin/php-cgi
51843  ??  I      7:29.32 /usr/local/bin/php-cgi
51851  ??  I      7:19.06 /usr/local/bin/php-cgi
59959  ??  Is     0:00.93 /usr/local/bin/php-cgi
67261  ??  I      6:31.64 /usr/local/bin/php-cgi
root@rowla:~katester# kill 51838
root@rowla:~katester# kill 51842
root@rowla:~katester# kill 51843
root@rowla:~katester# kill 51851
root@rowla:~katester# kill 59959
root@rowla:~katester# kill 67261
67261: No such process
root@rowla:~katester# ps -U katester
  PID  TT  STAT      TIME COMMAND
root@rowla:~katester#

(Looks to me like PHP had spawned bash, as bash went away while killing off the PHP processes.)

142.166.3.123 www.katester.net - [05/Sep/2007:13:37:02 -0400] "GET /blog/index.php/feed/ HTTP/1.1" 200 17637 "-" "radianrss-1.0"