ET MALWARE Possible SSH Linux.Fokirtor backchannel command

Query · suricata

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";
Raw source ET MALWARE Possible SSH Linux.Fokirtor backchannel command · Suricata
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Published by Emerging Threats Open ↗, licensed under BSD 3-Clause ↗. Line breaks added for readability; the rule is otherwise unchanged. 
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;
)

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