alert udp any any -> any 53 (
msg:"ET EXPLOIT Possible BIND9 DoS CVE-2015-5477 M2";
content:"|01 00 00 01|"; depth:4; offset:2;
content:"|00 01|"; distance:4; within:2;
pcre:"/^[^\x00]+\x00/R";
content:"|00 f9|"; within:2; fast_pattern;
pcre:"/^..[^\x00]+\x00/Rs";
content:!"|00 f9|"; within:2;
threshold:type limit, track by_src, seconds 60, count 1;
reference:cve,2015-5477;
classtype:attempted-dos;
sid:2021573; rev:4;
metadata:created_at 2015_08_01, cve CVE_2015_5477, confidence Medium, signature_severity Major, updated_at 2023_05_24;
)