In the context of computer software, a Trojan horse is a program that contains or installs a malicious program (sometimes called the payload or 'trojan'). The term is derived from the classical myth of the Trojan Horse. Trojan horses may appear to be useful or interesting programs (or at the very least harmless) to an unsuspecting user, but are actually harmful when executed.
More here: http://en.wikipedia.org/wiki/Trojan_horse_(computing)
I also can't find anything more about " 1und1_Haxdoor " as what you found - SpybotS&D Update 7. February 2007.
Does SpybotS&D come up clean ? How about Housecall - did it come up clean?
How about letting him download HJT and posting it on a HJT forum - this way, they can SEE if there is still "something" on his computer.
A friend in panic called me late last night -- Spybot found "1und1_Haxdoor trojan". According to him (he can barely find his way around a computer), the word "library" was also in the report. Spybot was able to remove in the first go-around. This "trojan" was on the Spybot 02/07 defs database, but other than that, I could not find anything about this particular "haxdoor" in my Search.
For my own information, I have three questions:
1, Was it an actual "trojan"?
2. If so, did Spybot clean out completely?
3. Why could I not find other references to it in my Search? Is it because he did not give me the entire name or that it had aliases?