alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Trojan.Vaklik.kku Checkin Response"; flow:from_server,established; flowbits:isset,et.trojan.valkik.kku; content:"Content-Length|3a 20|88|0d 0a|"; nocase; content:"|0d 0a 0d 0a|"; distance:0; content:"|48 00 00 00|"; distance:4; within:4; flowbits:unset,et.trojan.valkik.kku; reference:md5,9688d1d37a7ced200c53ec2b9332a0ad; reference:md5,81d8a235cb5f7345b5796483abe8145f; classtype:command-and-control; sid:2012961; rev:3; metadata:created_at 2011_06_09, signature_severity Major, updated_at 2019_07_26;)