alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE VNCStartServer USR Variant CnC Beacon"; flow:established,to_server; dsize:<100; content:"|00 00 00 19 00 00 00|"; offset:1; depth:7; content:"|01 00 00|"; distance:1; within:3; content:"USR-"; distance:1; within:4; fast_pattern; content:"|00|"; endswith; reference:md5,d66956e0ee70a60e19a4f310339d28a9; classtype:command-and-control; sid:2035523; rev:3; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2019_11_12, deployment Perimeter, confidence Medium, signature_severity Major, tag c2, updated_at 2019_12_02, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)