Or, say a user is using BitTorrent (http://www.bittorrent.com/) or some other P2P (peer-to-peer) program, which also uses listening services, to share files?
I'm sorry. I don't believe for a New York minute that this bug is so insignificant that Microsoft can just ignore it. I'll tell what I think is really going on here. I think Microsoft doesn't want to go to the trouble of securing XP when it would much, much rather have you upgrade, or try to upgrade anyway, to Windows 7.
Microsoft barely makes any money on XP sales, and it doesn't make a penny from updating it. If they can skip spending the money on fixing what they claim is a minor XP problem, why not? After all, it will let them claim that Windows 7 is more secure than XP so that will be another reason for you to 'upgrade' to Windows 7.
Oh, that reminds me. Windows 7 and networking? Microsoft has just confessed to having a killer, security hole in SMB (Server Message Block) 2, part of the fundamental Microsoft network file- and print-sharing protocol, that lets attackers knock out and/or hijack Vista, Server 2008, and the Windows 7 release candidates. What it doesn't do though is successfully attack Windows XP or 2000.
Oh the irony! You know folks, just a reminder, you can still switch the far safer desktop Linux operating systems or get a Mac.