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Backdoor used by attackers in Operation Cleaver

yara HIGH Yara-Rules
backdoorcommunity
This rule was pulled from an open-source repository and enriched with AI. Validate in a test environment before deploying to production.
View original rule at Yara-Rules →
Retrieved: 2026-05-31T23:00:00Z · Confidence: medium

Hunt Hypothesis

Attackers in Operation Cleaver are using a backdoor to maintain persistent access and exfiltrate data from compromised systems. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect and mitigate advanced persistent threats before significant data loss occurs.

YARA Rule

rule OPCLEAVER_csext
{

    meta:
        description = "Backdoor used by attackers in Operation Cleaver"
        reference = "http://cylance.com/assets/Cleaver/Cylance_Operation_Cleaver_Report.pdf"
        date = "2014/12/02"
        author = "Cylance Inc."
        score = "70"

    strings:
        $s1 = "COM+ System Extentions"
        $s2 = "csext.exe"
        $s3 = "COM_Extentions_bin"

    condition:
        all of them
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

This rule contains 3 string patterns in its detection logic.

References

False Positive Guidance

Original source: https://github.com/Yara-Rules/rules/blob/main/malware/APT_OPCleaver.yar