I just got finished with an involved effort to get rid of Downloader Trojan.
I somehow got this thing (Symantec says it comes in via email) back in late
August, according to the date on the file.

It wasn't caught by my Norton A/V coming in, or in numerous successive
scans. I assume it has a time release feature, only because it took from
late August until recently to manifest iteself.

I didn't know I had a problem until a few days ago when I started getting a
never ending flood of trashy pop up ads. They would come in groups, maybe
twice a day.

The Dowloader attempted to disable my Kerio firewall. It did jam it up, but
didn't hurt it any.

I had started working on finding out where my problem was, when Norton
alerted today (not during a scan). It took an iterative process to get rid
of the pest finally. The Trojan I had was a variant Norton couldn't
completely fix for me. I ended up having to go into registry to get rid of
the remnants of the Trojan.

Anyway, just thought I'd toss this out in case it may be of help to someone.

Also, I'd love to be able to email Norton (Symantec) and ask them why their
product didn't protect me on this one.

Anyone know an email address for Symantec? That seems to be one of the
world's best guarded secrets----like maybe the last thing they want is
someone to be able to communicate with them.

Spybot Search and Destroy (http://security.kolla.de) is remarkable effective
against this class of trojan.

I run Spybot and AdAware every couple of days. All these do for me is get
rid of the cookies the popups left behind.