alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"MALWARE [PTsecurity] Backdor.W32/Virut"; flow:established, to_server; dsize:<13; stream_size:server, <,400; stream_size:client, <,90; flowbits:isset, FB303766_2; flowbits:unset, FB303766_2; classtype:trojan-activity; metadata:created_at 2017_7_17; reference:url, github.com/ptresearch/AttackDetection; sid:11002264; rev:2;)