ICMP type 3 are messages generated by router in case of destination unreachable. Your servers try to connect to internet-servers directly but it may be impossible by network configuration.
Cisco IPS is able to detect and block web-server and other application level attacks. You may see web-based signatures in web category in IME/IDM interface or sort by http-related engine. You can also find their descriptions on page http://tools.cisc...
