alert tcp $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Backdoor.Win32.DarkComet Keepalive Inbound"; flow:from_server,established; dsize:<30; content:"KEEPALIVE"; nocase; depth:9; pcre:"/^KEEPALIVE\x7c?\d/i"; reference:url,www.microsoft.com/security/portal/Threat/Encyclopedia/Entry.aspx?Name=Backdoor%3aWin32%2fFynloski.A&ThreatID=-2147327112; reference:url,www.contextis.com/research/blog/darkcometrat/; classtype:trojan-activity; sid:2013091; rev:7; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2011_06_22, deployment Perimeter, performance_impact Low, signature_severity Major, updated_at 2019_07_26;)