alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Backdoor.Win32.DarkComet Keepalive Outbound"; flow:to_server,established; content:"KEEPALIVE"; depth:9; pcre:"/^KEEPALIVE\d+$/"; reference:md5,d4f949f268d00522cfbae5d18cbce933; classtype:trojan-activity; sid:2023091; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2016_08_25, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, updated_at 2019_07_26;)