alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET USER_AGENTS Observed Malicious CASPER/Mirai UA"; flow:established,to_server; http.user_agent; content:"Mozilla/4.0 (compatible|3b| MSIE 5.01|3b| Windows NT 5.0)"; bsize:63; fast_pattern; reference:url,www.blackberry.com/content/dam/blackberry-com/asset/enterprise/pdf/direct/report-bb-decade-of-the-rats.pdf; reference:md5,ea78869555018cdab3699e2df5d7e7f8; classtype:misc-activity; sid:2029892; rev:1; metadata:created_at 2020_04_13, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_04_13;)