The host at this IP address is being used as a Command&Control Server (C&C) for the ZeuS Trojan.
ZeuS (also known as zbot/WSNPoem is a banking Trojan used to steal credentials for online banking accounts from the victims computer:

McAfee: http://vil.nai.com/vil/content/v_255218.htm
Symantec: http://www.symantec.com/security_response/writeup.jsp?docid=2010-011016-3514-99

$ dig tuk-tuk.com +short @8.8.8.8
203.121.165.16

ZeuS C&C is located at 203.121.165.16:

IP Address : 203.121.165.16
AS number : AS4765
AS description : WORLDNET-AS World Net & Services Co., Ltd.

tuk-tuk.com has address 203.121.165.16

tuk-tuk.com/map/Icons/Religion/brah.png (config)
tuk-tuk.com/map/Icons/Religion/exejfjfjexe.exe (binary)

More information about this malware:
MD5 hash: 2635e89edbc4458497a970c29bf3b092
-> Anubis: http://anubis.iseclab.org/?action=result&task_id=15d598923f7783ba479a9edcd533cb013

More information on ZeuS Tracker

To have record SBL107339 (203.121.165.16/32) removed from the SBL, the Abuse/Security representative of pacific.net.th (or the Internet Service Provider responsible for supplying connectivity to 203.121.165.16/32) needs to contact the SBL Team by email (use this link) to explain how the spam problem has been terminated (we need to know exactly how the issue has been dealt with and that this spam problem is fully terminated). If the spam problem that caused this listing has been terminated we will normally remove the listing from the SBL without delay.

It is essential that emails to the SBL Team about this SBL listing include this exact ticket information in the email Subject:

If you are a representative of pacific.net.th, you also need to see: Current Live pacific.net.th SBL Listings