The fact that attempts are being made to connect to your computer by programs looking for systems infected by a Trojan does not mean that you are infected. All computers connected to the Internet get bombarded each day by various bots which are looking to see which systems are vulnerable.
If several different Trojan-detection programs say your system is clean, then it is likely they are right and you are just getting a lot of knocks on your virtual door. Ignore them.
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This was first published in April 2002