ICMP Destination Unreachable Port Unreachable

My SNORT installation set of an alarm a few days back:

"ICMP Destination Unreachable Port Unreachable" [Impact: Vulnerable] From "SNORT-sensor" at Thu Dec 13 13:24:59 2007 UTC [Classification: Misc Activity] [Priority: 3] {icmp} RemoteHostIP->LocalHostIP

I have checked my firewall logs and confirmed that the LocalHost has been trying to connect to RemoteHost at that time and also checked a pcap-file from snort and found my LocalHost MAC-adress so it's not somekind of spoofing. The problem here is that the RemoteHost is NOT anything I want to talk to.

I have scanned the LocalHost with several antivirus/antirootkit/antispyware byt can't find anything that could cause the connectionattempts.

Has anyone seen anything like this before? What could possibly cause this? Is my LocalHost compromised?


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