alert tcp $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE VirRansom/VirLock Checkin Response"; flow:established,from_server; dsize:4; content:"|74 01 00 00|"; fast_pattern; flowbits:isset,ET.VirLock; reference:md5,fbeb6ebd498d85b1f404d7bb4acc3b89; classtype:command-and-control; sid:2019902; rev:2; metadata:created_at 2014_12_10, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_10_08;)