alert udp $EXTERNAL_NET any -> $HOME_NET 69 (msg:"GPL TFTP NULL command attempt"; content:"|00 00|"; depth:2; reference:bugtraq,7575; classtype:bad-unknown; sid:2102336; rev:4; metadata:created_at 2010_09_23, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_07_26;)