alert tcp $EXTERNAL_NET any -> $HOME_NET 1024: (msg:"ET MALWARE Possible XServer Backdoor Certificate Observed"; flow:established,to_server; content:"|16|"; depth:1; content:"|55 04 06|"; distance:0; content:"|02|US|31|"; distance:1; within:4; content:"|55 04 08|"; distance:0; content:"|02|BA|31|"; distance:1; within:4; content:"|55 04 0a|"; distance:0; content:"|04|Root|31|"; distance:1; within:6; content:"|55 04 0b|"; distance:0; content:"|04|Root|31|"; distance:1; within:6; fast_pattern; content:"|55 04 03|"; distance:0; content:"|04|Root|30|"; distance:1; within:6; reference:url,resources.fox-it.com/rs/170-CAK-271/images/201912_Report_Operation_Wocao.pdf; classtype:command-and-control; sid:2029190; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2019_12_23, deployment Perimeter, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_12_23;)