alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE NCSC XAgent Beacon"; flow:established,to_server; content:"HTTP/1.1|0d 0a|Accept|3a|text/html,application/xhtml+xml,application/xml|3b|q=0.9,*"; content:!"Host|3a| yandex.ru"; pcre:"/^(?:GET|POST)\/(?:watch|search|find|results|open|search|close)\/\?(?:text=|from=|aq=|ai=|ags=|oe=|btnG=|oprnd=|utm=|channel=|itwm=)/"; reference:url,www.ncsc.gov.uk/content/files/protected_files/article_files/IOC-APT28-malware-advisory.pdf; classtype:targeted-activity; sid:2026437; rev:1; metadata:attack_target Client_Endpoint, created_at 2018_10_04, deployment Perimeter, confidence Medium, signature_severity Major, tag c2, updated_at 2019_07_26, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)