I'm new to security and am finding several deined on inside interface access-list for ICMP (type 0 , code 0) from inside host > outside host. This is happening 24hr a day. The only thing I can see in log
is we are experencing ping sweeps from this IP block.
I have ran several trojan and virus scans from several different venders and return nothing on the inside host.
Is this a normal response from a inside host with a public interface on a single port? I do not allow icmp from internal host.
ICMP type 0 is ECHO-Reply. It seems like your inside hosts are sending lot of replies as a result of ECHO (Ping). We have seen this behavoiur as a result of the recent worms e.g. NACHI/BLASTER. If you are seeing this syslog message alot, you better need to apply access-list on the inside interface to block it, additionaly you need to inspect your hosts for the possibility of worms.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...