alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Sage Ransomware Checkin"; flow:established,from_server; flowbits:isset,ET.Sage.Primer; http.header; content:"Content-Length|3a 20|1|0d 0a|"; file.data; content:"k"; within:1; endswith; reference:url,isc.sans.edu/forums/diary/Sage+20+Ransomware/21959; classtype:command-and-control; sid:2023767; rev:4; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2017_01_25, deployment Perimeter, malware_family Ransomware, malware_family Sage, confidence High, signature_severity Major, tag Ransomware, updated_at 2020_09_14, mitre_tactic_id TA0040, mitre_tactic_name Impact, mitre_technique_id T1486, mitre_technique_name Data_Encrypted_for_Impact;)