Anthropic-Cybersecurity-Skills/skills/detecting-business-email-compromise/SKILL.md

name, description, domain, subdomain, tags, version, author, license, atlas_techniques, nist_ai_rmf, d3fend_techniques, nist_csf, mitre_attack, mitre_f3

name	description	domain	subdomain	tags	version	author	license	atlas_techniques	nist_ai_rmf	d3fend_techniques	nist_csf	mitre_attack	mitre_f3
detecting-business-email-compromise	Detect Business Email Compromise (BEC) fraud, where attackers impersonate executives or vendors to trick employees into wire transfers or data disclosure without malicious links, using email gateway rules, behavioral analytics, and financial process controls. Use when investigating a suspected executive/vendor impersonation email or building detection rules for social-engineering fund-transfer fraud.	cybersecurity	phishing-defense	phishing email-security social-engineering dmarc awareness bec fraud	1.0	mahipal	Apache-2.0	AML.T0052 AML.T0088	GOVERN-6.2 MAP-5.2	Restore Object Restore Configuration Application Configuration Hardening Application Hardening Disable Remote Access	PR.AT-01 DE.CM-09 RS.CO-02 DE.AE-02	T1566.002 T1534 T1114.002 T1657 T1078.004	version tactics techniques 1.1 initial-access positioning monetization stealth id name tactic source T1672 Email Spoofing stealth attack id name tactic source F1032 Impersonate Official initial-access f3 id name tactic source F1036 New Vendor Setup positioning f3 id name tactic source F1005.006 Account Manipulation: Change of Payment Details positioning f3 id name tactic source F1025.003 Electronic Funds Transfer: Wire Transfer monetization f3 id name tactic source F1022 Delete Relevant Emails stealth f3

Detecting Business Email Compromise

Overview

Business Email Compromise (BEC) is a sophisticated fraud scheme where attackers impersonate executives, vendors, or trusted partners to trick employees into transferring funds, sharing sensitive data, or changing payment details. Unlike traditional phishing, BEC often contains no malicious links or attachments, relying purely on social engineering. This skill covers detection techniques using email gateway rules, behavioral analytics, and financial process controls.

When to Use

• When investigating security incidents that require detecting business email compromise
• When building detection rules or threat hunting queries for this domain
• When SOC analysts need structured procedures for this analysis type
• When validating security monitoring coverage for related attack techniques

Prerequisites

• Email security gateway with BEC detection capabilities
• Understanding of organizational financial processes and approval chains
• Access to email logs and SIEM platform
• Knowledge of social engineering tactics

Key Concepts

BEC Attack Types (FBI IC3 Classification)

1. CEO Fraud: Attacker impersonates CEO, requests urgent wire transfer
2. Account Compromise: Employee email compromised, used to request payments from vendors
3. False Invoice Scheme: Fake invoices from "vendor" with changed bank details
4. Attorney Impersonation: Impersonates legal counsel for urgent confidential transfers
5. Data Theft: Requests W-2, tax forms, or PII from HR

Detection Indicators

• Urgency and secrecy language ("confidential", "do not discuss with others")
• New or changed payment instructions
• Executive communication outside normal patterns
• Display name matches executive but email domain differs
• Reply-to address differs from From address
• First-time communication pattern between sender and recipient
• Request for gift cards or cryptocurrency

Workflow

Step 1: Configure BEC-Specific Email Rules

• Flag emails with VIP display names from external domains
• Detect financial keywords combined with urgency language
• Alert on first-time sender to finance/accounting staff
• Check for Reply-To domain mismatch

Step 2: Deploy Behavioral Analytics

• Baseline normal communication patterns per user
• Detect anomalous requests (unusual recipient, unusual time, unusual request type)
• Monitor for email forwarding rule changes (T1114.003)

Step 3: Implement Financial Controls

• Dual-authorization for wire transfers above threshold
• Out-of-band verification for payment detail changes (phone callback)
• Vendor payment change verification process
• Finance team training on BEC red flags

Step 4: Monitor for Account Compromise

• Detect impossible travel in email login locations
• Alert on email forwarding rule creation
• Monitor for mailbox delegation changes
• Check for inbox rules hiding BEC-related emails

Tools & Resources

• Microsoft Defender for O365 Anti-BEC: Built-in BEC detection
• Proofpoint Email Fraud Defense: BEC-specific solution
• Abnormal Security: AI-driven BEC detection
• FBI IC3 BEC Advisory: https://www.ic3.gov/
• FinCEN BEC Advisory: Financial institution guidance

Validation

• BEC detection rules trigger on test scenarios
• Financial controls prevent unauthorized transfers in drills
• Account compromise detection catches simulated attacks
• Reduced BEC susceptibility in awareness assessments