ET WEB_SERVER LEMURLOOT WebShell Interaction Header - X-siLock-Step1 -1 Data Exfil Response - Observed in MOVEit File Transfer - OUTBOUND (Active Compromise)

alert http [$HOME_NET,$HTTP_SERVERS] any -> $EXTERNAL_NET any (
    msg:"ET WEB_SERVER LEMURLOOT WebShell Interaction Header - X-siLock-Step1 -1 Data Exfil Response - Observed in MOVEit File Transfer - OUTBOUND (Active Compromise)";
    flow:established,to_client;
    http.header_names;
    content:"|0d 0a|X-siLock-Comment|0d 0a|";
    content:"|0d 0a|AzureBlobStorageAccount|0d 0a|";
    content:"|0d 0a|AzureBlobKey|0d 0a|";
    content:"|0d 0a|AzureBlobContainer|0d 0a|"; fast_pattern; nocase;
    reference:url,www.huntress.com/blog/moveit-transfer-critical-vulnerability-rapid-response;
    reference:url,community.progress.com/s/article/MOVEit-Transfer-Critical-Vulnerability-31May2023;
    reference:md5,af136505d384c9a89635b365e55b7fa3;
    reference:url,www.mandiant.com/resources/blog/zero-day-moveit-data-theft;
    classtype:successful-admin;
    sid:2046050; rev:1;
    metadata:attack_target Web_Server, created_at 2023_06_02, deployment Perimeter, deployment SSLDecrypt, malware_family LEMURLOOT, performance_impact Low, confidence High, signature_severity Critical, tag WebShell, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_06_02;
    target:src_ip;
)