alert icmp $EXTERNAL_NET any -> $HOME_NET any (msg:"GPL SCAN Nemesis v1.1 Echo"; dsize:20; icmp_id:0; icmp_seq:0; itype:8; content:"|00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00|"; reference:arachnids,449; classtype:attempted-recon; sid:2100467; rev:5; metadata:created_at 2010_09_23, confidence High, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_07_26;)