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.