Rule History

alert tcp $EXTERNAL_NET any -> any 22 (msg:"ET MALWARE Possible SSH Linux.Fokirtor backchannel command"; flow:established,to_server; content:"|3a 21 3b 2e|"; pcre:"/^(?:[A-Za-z0-9\+\/]{4})*(?:[A-Za-z0-9\+\/]{2}==|[A-Za-z0-9\+\/]{3}=|[A-Za-z0-9\+\/]{4})/R"; reference:url,www.symantec.com/connect/blogs/linux-back-door-uses-covert-communication-protocol; classtype:trojan-activity; sid:2017727; rev:6; metadata:created_at 2013_11_16, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_07_26;)