Detects the possible extortion scam on the basis of subjects and keywords

Hunt Hypothesis

Adversaries may use specific subjects and keywords in communication to mimic extortion scams and manipulate victims into paying ransoms. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify potential social engineering attempts early and prevent financial loss.

YARA Rule

rule extortion_email
{
  meta:
    author = "milann shrestha <Twitter - @x0verhaul>"
		description = "Detects the possible extortion scam on the basis of subjects and keywords"
		data = "12th May 2020"

	strings:
	  $eml1="From:"
    $eml2="To:"
    $eml3="Subject:"
		
		// Common Subjects scammer keep for luring the targets 
    $sub1 = "Hackers know password from your account."
    $sub2 = "Security Alert. Your accounts were hacked by a criminal group."
    $sub3 = "Your account was under attack! Change your credentials!"
    $sub4 = "The decision to suspend your account. Waiting for payment"
    $sub5 = "Fraudsters know your old passwords. Access data must be changed."
    $sub6 = "Your account has been hacked! You need to unlock it."
    $sub7 = "Be sure to read this message! Your personal data is threatened!"
    $sub8 = "Password must be changed now."

		// Keywords used for extortion
    $key1 = "BTC" nocase
    $key2 = "Wallet" nocase
    $key3 = "Bitcoin" nocase
    $key4 = "hours" nocase
    $key5 = "payment" nocase
    $key6 = "malware" nocase
    $key = "bitcoin address" nocase
    $key7 = "access" nocase
    $key8 = "virus" nocase

	condition: 
    all of ($eml*) and
    any of ($sub*) and
    any of ($key*)
}

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 20 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: Scheduled System Backup Job
  Description: A legitimate scheduled backup job (e.g., vssadmin or wbadmin on Windows, rsync or tar on Linux) is executing and includes terms like “extortion” or “ransom” in its log or script name.
  Filter/Exclusion: Exclude processes associated with backup tools or jobs running during scheduled maintenance windows. Example: process.name = "wbadmin" OR process.name = "rsync"

• Scenario: User-Initiated File Search
  Description: An admin or user is searching for files containing keywords like “extortion” or “ransom” using tools like find, grep, or Get-ChildItem in PowerShell for compliance or audit purposes.
  Filter/Exclusion: Exclude processes initiated by users with elevated privileges or those using search tools with known compliance-related patterns. Example: process.name = "find" OR process.name = "grep" OR user.name = "admin"

• Scenario: Email Archiving or Compliance Task
  Description: An email archiving tool (e.g., Microsoft Exchange Online Archiving, Symantec Enterprise Vault) is processing emails and includes terms like “extortion” or “ransom” in the subject or body.
  Filter/Exclusion: Exclude emails processed by archiving tools or those flagged as part of a compliance or legal hold. Example: email.subject = "Archiving" OR email.tool = "Enterprise Vault"

• Scenario: Security Software Scan
  Description: A security tool (e.g., CrowdStrike, CrowdStrike Falcon, or Microsoft Defender) is scanning for malware and includes terms like “extortion” or “ransom” in its scan log or alert message.
  Filter/Exclusion: Exclude processes related to security software or scan activities. Example: `