alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Wintervivern Activity (GET)"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"vivern/"; fast_pattern; content:".xml"; endswith; http.header_names; content:!"Referer"; reference:url,www.domaintools.com/resources/blog/winter-vivern-a-look-at-re-crafted-government-maldocs; reference:url,lab52.io/blog/winter-vivern-all-summer/; reference:md5,7940c343ae91e7198acf83400b25252f; classtype:trojan-activity; sid:2034105; rev:1; metadata:attack_target Client_Endpoint, created_at 2021_10_04, deployment Perimeter, deployment SSLDecrypt, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_10_04;)