alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/Ursnif Connectivity Check"; flow:established,to_server; urilen:21; http.method; content:"GET"; http.uri; content:"/proto/netstrings.txt"; http.header_names; content:!"Accept"; content:!"Referer|0d 0a|"; reference:md5,9134651a7c642798414d867874bdfe2f; reference:url,csis.dk/en/csis/news/4472/; classtype:trojan-activity; sid:2019381; rev:4; metadata:created_at 2014_10_09, malware_family Win32_Ursnif, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_05_12;)