NAT translation table

I've gone to Cisco's web site trying to get information on this but have not received much significant help. Maybe someone here can help me out.

When looking at the NAT translation table on my Cisco 1700 I see a number of translations between outside addresses and my http port 80. However, I show no activity on web server logs that indicates someone is hitting my web server. Is this some sort of scan for vulnerabilities that is not detected by the web logs? Could it possibly be more serious? Thanks for any help anyone can offer.

What exactly does your webserver log? Maybe these are simple portscans, not picked up by the weblog, because no pages were transmitted?

The web server logs any http commands (GET, POST, etc.). I can see scans all day long made for common vulnerabilities of MS IIS but they are not coming from the same IP as the outside translation IP on NAT.

does the ip scan other ports as well? does it resolve to some known hostname? ... I'm fishing in the dark here... (hey, some network guru, help us out here)

No, it only seems to scan port 80. There are a couple of other open ports that could be scanned.

I don't know it this helps any but I do occasionally get an entry in my web log such as:
x.x.x.x - (CurrentDate) - "GET http://www.hostname.com/ HTTP/1.1" 200 3059. I'm not open to being a proxy that I know of but it seems someone is trying to access another site through my http port. Maybe its related?

PacSec

What version IOS is built on your router/firewall? Also how did you configure your static nat statements? And last, could you post a small portion of the show ip nat trans?

I have IOS version 12.2-7a. My static nat is as follows:
ip nat inside source static tcp x.x.x.x (inside address) 80 y.y.y.y (outside address) 80 extedable
(That is for the http server. I have ports 25 and 110 set up the same way.)
As far as the show ip nat trans, it looks basically like this

Pro Inside global Inside local Outside local Outside global
tcp y.y.y.y:80 x.x.x.x:80 a.a.a.a:14721 a.a.a.a:14721
tcp y.y.y.y:80 x.x.x.x:80 b.b.b.b:13193 b.b.b.b:13193
tcp y.y.y.y:80 x.x.x.x:80 b.b.b.b:47260 b.b.b.b:47260

This is just a quick sample. Where the letters representing the ip address are the same, the ips are the same. As you can see one ip will sometimes have open a couple of its ports to my port 80. Other times, there is only one open port to my port 80.

ok this might be totally off, but you could just be seeing nimda scans.

I'm pretty sure the nimda scans are showing up on the web server access log.

Doing PAT you will receive multiple entries which a person is connecting to you and opening multiple ports. This is normal.
First off, I would turn off IP Fast Switching (no ip route-cache) on all the nat inside/outside interfaces if its not already turned off. The two dont work well together, and always saw various issues when the two worked together. Second, I would add a packet sniffer to your network and verify the packets are indeed accessing your LAN, or if its just a small bug in which the cisco router is generating the information you are seeing.
Now I havent really read much on the Code Red virus, but I know it sends a GET request to your port 80 server. Maybe if you have the patch, the server blocks the GET request attempts in which it doesnt show anyone accessing your web server.