OT: MS Server Question, HELP!, calling on the geeks ... Options

[SirAndy]

sooo, on one (actually 2) of our servers running IIS, we get a lot of hack attempts lately. they're all of the same type, buffer overflow attacks on port 80.

i have all the latest security patches (Windows NT 4) and they are NOT compromising the box, that's the good news.

the bad news is, that lately, the type of attack has slightly changed and now they succeed in crashing IIS!

so here's the problem:
this box (or 2) run important eCommerce websites for me so closing port 80 or moving to another port is NOT an option.
moving to another OS is NOT an option. banning IP's is NOT a option (most of those kids are on dialup DSL, so i would have to block a whole range, most likely cutting out legit customers)
how can i run those websites without having IIS die on me a couple of times a day?

the only thing i can think of is to implement some sort of content filtering that removes malicious code before it gets to the web-server.
anyone here who has a running example of a setup like that?
what (good) firewalls have that sort of filtering and how much do they cost?

i'm at the end of the rope here ... (IMG:style_emoticons/default/fighting19.gif)
Andy

[boxsterfan]

There are several tricks, but some copies of the IISlogs to see exactly what they are doing would be helpful.

1. Run IISLockdown
2. Remove any of the defaults installed with IIS (default web site, etc..)
3. File permissions
4. Install a Host-based IDS
5. Install AntiVirus
6. Have enough RAM?
7. Are you sure you have all the patches on?
8. Upgrade to WIN2K with IIS 5.0 (much more stable web server, but still requires patching)

I work in the financial industry. http://www.visa.com/cisp has many requirements to help lock down systems.

Do you have a custom ISAPI DLL crashing the box? Need more info on your setup.