Trojans do not attack from the internet, they attack from the inside.

I would hazard a guess that NIS keeps popping up with some type of warning along the lines of, "sub7 trojan hourse attack detected".

This is just the firewall part if NIS doing it's job, stopping attemps to connect to your pc. Infact they are probably not attemps to connect at all, but rather scans looking for pc's that are infected with what ever trojan. As such nothing to be alarmed about.

On the other hand you could possibly be infected. So run some av/malware scans to be sure. Don't limit your self to just NAV, use Trend Micro's House call, an online scan.

http://housecall.trendmicro.com/hous...start_corp.asp

Download install and run. Spybot search and destroy, Lavasoft's Adaware, MoosoftsThe Cleaner, Tds3. These are all found easily using google. Or indead looking through some of the posts here at AO where there may already be a link.