detecting-business-email-compromise

name	detecting-business-email-compromise
description	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,
domain	cybersecurity
subdomain	phishing-defense
tags	["phishing","email-security","social-engineering","dmarc","awareness","bec","fraud"]
version	1.0
author	mahipal
license	Apache-2.0
atlas_techniques	["AML.T0052","AML.T0088"]
nist_ai_rmf	["GOVERN-6.2","MAP-5.2"]
d3fend_techniques	["Restore Object","Restore Configuration","Application Configuration Hardening","Application Hardening","Disable Remote Access"]
nist_csf	["PR.AT-01","DE.CM-09","RS.CO-02","DE.AE-02"]

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

Detection Gaps & Validation

• SPF passes but the sender is spoofed: a cousin domain or free-webmail account passes SPF/DKIM/DMARC for ITS OWN domain while the display name reads "CFO" - auth "pass" does not mean the brand is genuine. Alert on VIP display name + external/free domain.
• No malicious payload: pure-text BEC has no URL/attachment to detonate, so sandboxes are blind - lean on Reply-To mismatch, first-contact-to-finance, and payment-change keyword + urgency rules.
• False-invoice / bank-change: the highest-loss variant changes vendor banking details inside a real-looking thread - require out-of-band callback verification, not email confirmation.
• Account compromise is internal: mail originates from a real mailbox, so all reputation/auth checks pass - detect via inbox-rule creation (T1114.003), impossible travel, and auto-forward rules hiding replies.
• Lookalike domains: add homoglyph detection (rn->m, capital-I/lowercase-l) against your domain and top vendors.
• Validate + FP tuning: run BEC test scenarios (CEO gift-card, vendor bank change, W-2 request) and confirm rules trigger; whitelist legitimate first-time senders (recruiters, new vendors) by role to keep finance/AP alerts low-noise.

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