ET MALWARE Inbound PowerShell Saving Base64 Decoded Payload to Temp M1 2018-11-29

alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"ET MALWARE Inbound PowerShell Saving Base64 Decoded Payload to Temp M1 2018-11-29";
    flow:established,from_server;
    http.stat_code;
    content:"200";
    file.data;
    content:"|3a 3a|FromBase64String|28|"; nocase;
    content:"Set-Content"; distance:0; nocase;
    content:"C|3a 5c|Windows|5c|Temp"; distance:0; nocase; fast_pattern;
    content:"-Encoding"; distance:0; nocase;
    content:"|0a 0a 0a|";
    pcre:"/^(?P<js>\$[a-z0-9]{1,15})\s*=\s*\[System\.Text\.Encoding\]::ASCII\.GetString\(\[System\.Convert\]::FromBase64String\((?P=js)\)\)\s*Set-Content\s*(?:-Path\s*C:\\Windows\\Temp\\[a-z0-9]{1,15}\.[a-z0-9]{2,4}\s*|-Value\s*(?P=js)\s*|-Encoding\s*ASCII){3}/Ri";
    reference:url,www.clearskysec.com/muddywater-operations-in-lebanon-and-oman/;
    classtype:trojan-activity;
    sid:2026675; rev:3;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2018_11_29, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag PowerShell, tag Obfuscated, updated_at 2020_08_27;
)