FinFisher FinSpy

Hunt Hypothesis

This hypothesis posits that adversaries are deploying FinFisher (FinSpy) to establish persistent command-and-control channels and exfiltrate sensitive financial data via covert network traffic patterns. Proactive hunting in Azure Sentinel is critical because this low-severity indicator often represents early-stage reconnaissance that, if unaddressed, could evolve into a high-impact breach within the organization’s cloud infrastructure.

YARA Rule

rule FinSpy
{
    meta:
        description = "FinFisher FinSpy"
        author = "AlienVault Labs"

    strings:
        $filter1 = "$password14"
        $filter2 = "$screenrec7"
        $filter3 = "$micrec"
        $filter4 = "$skyperec3"
        $filter5 = "$mouserec2"
        $filter6 = "$driver"
        $filter7 = "$janedow2"
        $filter8 = "$bootkit2"

        $password1 = /\/scomma kbd101\.sys/ wide ascii
        $password2 = /(N)AME,EMAIL CLIENT,EMAIL ADDRESS,SERVER NAME,SERVER TYPE,USERNAME,PASSWORD,PROFILE/ wide ascii
        $password3 = /\/scomma excel2010\.part/ wide ascii
        $password4 = /(A)PPLICATION,PROTOCOL,USERNAME,PASSWORD/ wide ascii
        $password5 = /\/stab MSVCR32\.manifest/ wide ascii
        $password6 = /\/scomma MSN2010\.dll/ wide ascii
        $password7 = /\/scomma Firefox\.base/ wide ascii
        $password8 = /(I)NDEX,URL,USERNAME,PASSWORD,USERNAME FIELD,PASSWORD FIELD,FILE,HTTP/ wide ascii
        $password9 = /\/scomma IE7setup\.sys/ wide ascii
        $password10 = /(O)RIGIN URL,ACTION URL,USERNAME FIELD,PASSWORD FIELD,USERNAME,PASSWORD,TIMESTAMP/ wide ascii
        $password11 = /\/scomma office2007\.cab/ wide ascii
        $password12 = /(U)RL,PASSWORD TYPE,USERNAME,PASSWORD,USERNAME FIELD,PASSWORD FIELD/ wide ascii
        $password13 = /\/scomma outlook2007\.dll/ wide ascii
        $password14 = /(F)ILENAME,ENCRYPTION,VERSION,CRC,PASSWORD 1,PASSWORD 2,PASSWORD 3,PATH,SIZE,LAST MODIFICATION DATE,ERROR/ wide ascii

        $screenrec1 = /(s)111o00000000\.dat/ wide ascii
        $screenrec2 = /(t)111o00000000\.dat/ wide ascii
        $screenrec3 = /(f)113o00000000\.dat/ wide ascii
        $screenrec4 = /(w)114o00000000\.dat/ wide ascii
        $screenrec5 = /(u)112Q00000000\.dat/ wide ascii
        $screenrec6 = /(v)112Q00000000\.dat/ wide ascii
        $screenrec7 = /(v)112O00000000\.dat/ wide ascii

        //$keylogger1 = /\<%s UTC %s\|%d\|%s\>/ wide ascii
        //$keylogger2 = /1201[0-9A-F]{8}\.dat/ wide ascii

        $micrec = /2101[0-9A-F]{8}\.dat/ wide ascii

        $skyperec1 = /\[%19s\] %25s\:    %s/ wide ascii
        $skyperec2 = /Global\\\{A48F1A32\-A340\-11D0\-BC6B\-00A0C903%\.04X\}/ wide
        //$skyperec3 = /(1411|1421|1431|1451)[0-9A-F]{8}\.dat/ wide ascii

        //$mouserec1 = /(m)sc183Q000\.dat/ wide ascii
        //$mouserec2 = /2201[0-9A-F]{8}\.dat/ wide ascii

        $driver = /\\\\\\\\\.\\\\driverw/ wide ascii

        $janedow1 = /(J)ane Dow\'s x32 machine/ wide ascii
        $janedow2 = /(J)ane Dow\'s x64 machine/ wide ascii

        //$versions1 = /(f)inspyv2/ nocase
        //$versions2 = /(f)inspyv4/ nocase

        $bootkit1 = /(b)ootkit_x32driver/
        $bootkit2 = /(b)ootkit_x64driver/

        $typo1 = /(S)creenShort Recording/ wide

        $mssounddx = /(S)ystem\\CurrentControlSet\\Services\\mssounddx/ wide

    condition:
        (8 of ($password*) or any of ($screenrec*) or $micrec or any of ($skyperec*) or $driver or any of ($janedow*) or any of ($bootkit*) or $typo1 or $mssounddx) and not any of ($filter*)
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 46 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the FinFisher FinSpy detection rule in an enterprise environment, including suggested filters and exclusions:

• Endpoint Protection Scanning of Legacy Archives

  • Scenario: The organization’s endpoint protection suite (e.g., CrowdStrike Falcon or Microsoft Defender for Endpoint) performs a deep scan of large, legacy .zip or .tar archives containing historical financial data. These archives often contain embedded executable stubs that mimic the FinSpy payload structure, triggering the detection logic when the AV engine extracts and analyzes them in memory.
  • Filter/Exclusion: Exclude file paths matching known archive storage locations (e.g., C:\Data\Archives\*) from the specific “embedded executable” check within the rule, or add a signature exclusion for the AV scanner’s extraction process (mpcmdrun.exe or csagent.exe).

• Scheduled Software Deployment via SCCM

  • Scenario: A nightly scheduled task managed by Microsoft System Center Configuration Manager (SCCM) deploys a standard enterprise browser update. The deployment package includes a silent installer that creates temporary registry keys and modifies the Windows Registry under HKLM\SOFTWARE\Policies in a manner identical to FinSpy’s persistence mechanism, causing the rule to flag the SCCM client service (ccmexec.exe) as suspicious.
  • Filter/Exclusion: Whitelist the specific process name ccmexec.exe when it initiates registry modifications during the defined maintenance window (e.g., 02:00–04:00 UTC), or exclude the specific registry paths used by SCCM deployments from the rule’s scope.

• Third-Party HR Analytics Tool Installation

  • Scenario: The IT department installs a legitimate third-party analytics agent, such as ServiceNow Employee Experience or **Ok