alert tcp-pkt $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE BackConnect CnC Activity (Start VNC) M2"; flow:established,to_client; flowbits:isset,ET.BackConnect; content:"|1f 8b 08 08 05|"; startswith; dsize:13; threshold:type limit,track by_src,count 1,seconds 300; reference:url,netresec.com/?page=Blog&month=2022-10&post=IcedID-BackConnect-Protocol; reference:url,twitter.com/netresec/status/1577966512459087874; reference:url,twitter.com/Unit42_Intel/status/1577773890012594177; classtype:command-and-control; sid:2050087; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2024_01_16, deployment Perimeter, malware_family BackConnect, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_01_16;)