BEC is one of the most financially damaging forms of cybercrime today — exploiting trust, context, and timing rather than malware. In this consolidated guide, we’ll break down the major BEC attack flows, show real-world case studies, and provide detection and prevention playbooks for your teams.

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BEC & Invoice Fraud Explained

Business Email Compromise (BEC) is one of the most financially damaging cyber threats.
It doesn’t rely on malware or exploits — just trust, timing, and a well-crafted email.

This section explains how BEC works, especially through invoice fraud and impersonation tactics, and how to spot it before money leaves the account.

What Is BEC?

BEC is a targeted social engineering attack where cybercriminals impersonate a trusted party — usually a CEO, CFO, or vendor — to trick employees into:

• Sending payments to attacker-controlled bank accounts
• Changing payroll details
• Sharing sensitive financial data

Unlike phishing, BEC emails are often free of links or malware. They’re clean, convincing, and personalized.

Common BEC Variants

1. CEO Fraud / Executive Impersonation
2. Vendor Invoice Fraud
3. Payroll Redirect
4. Compromised Email Thread Hijack

Multi-Staged BEC Attacks

Attackers often draw out BEC over days or weeks, monitoring threads, mimicking workflows, and striking when payment is expected.

Why It Works:

• Invoice matches context
• Branding and tone feel real
• Multiple reinforcing emails
• Timing is perfect

Real-World Example

“Attached is our latest invoice … please note new banking details due to an audit.”

The victim processes the payment, believing it’s genuine.

Red Flags

• Requests to change banking info
• Slightly altered sender domains
• Urgent tone outside business hours
• Thread hijacking with unexpected invoices

Prevention & Mitigation

• Always verify banking changes via a separate channel
• Implement dual approvals for transfers
• Monitor mailbox rules and spoofed domains
• Enable DMARC, SPF, DKIM

Key Takeaway: Invoice Fraud

• Clean, malware-free emails
• Executive/vendor impersonation common
• Multi-staged, highly contextual
• Always confirm changes via a second channel

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BEC Vendor Hijack Case Study

A vendor email account gets compromised. Days or weeks later, the attacker strikes, right from inside the vendor’s real inbox, replying in a genuine thread.

What Happened

• Vendor’s Microsoft 365 compromised
• Forwarding rules set up to monitor finance emails
• PDF invoices altered with new banking details
• Sent directly inside real threads
• Follow-up “reminders” added credibility

Technical Clues Missed

• Hidden forwarding rule
• Invoice last edited from outside IP
• No DMARC enforcement
• No secondary verification of banking changes

Lessons Learned

• Even genuine threads can be poisoned
• Payment processes must be trusted, not just senders
• Quiet mailbox rules are compromise signals
• Finance teams need a payment-change checklist

Key Takeaway: Vendor Hijack

• Real accounts, real threads — but poisoned
• Forwards and rules are red flags
• Process verification is stronger than trust

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BEC Payroll Redirection Flow

Payroll redirect scams are among the simplest but most damaging forms of BEC.

Typical Flow

1. HR receives a spoofed/compromised email
2. Request: “Update my bank details immediately”
3. Attacker-controlled account added
4. Payroll processed — employee never receives pay

Email Style

Short, urgent, personal:

“I changed banks, please update my deposit for this cycle.”

Variants

• Asking process questions first
• Using fake forms/PDFs
• Multi-stage supervisor confirmations

Prevention

• Never accept banking changes over email
• Use a secure HR portal for updates
• Train HR/payroll teams on these tactics
• Monitor for employee impersonation domains

Key Takeaway: Payroll Fraud

• Low-effort, high-damage attacks
• Simple verification steps stop them
• Standardized secure HR processes are essential

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BEC Detection Playbook for SMBs

BEC is stealthy, targeted, and not easily caught by antivirus or firewalls.
For SMBs, defense relies on people and process.

Detecting Signs

• Sudden requests to change payment details
• Emails pushing secrecy or urgency
• Unexpected attachments or invoice edits
• Logins from suspicious IPs
• Hidden forwarding rules

Prevention Is the Best Detection

• Train finance/HR teams
• Require dual verification for banking changes
• Use banners for external emails
• Block/lookout for lookalike domains

What to Log & Monitor

• New inbox rules
• Foreign logins
• Failed login attempts
• Suspicious PDF metadata
• Sudden MFA removals

Response Plan

• Payment verification checklist
• Known-good vendor contact directory
• Process to pause payments if fraud suspected
• Bank escalation and insurance protocols

Key Takeaway: Detection Playbook

• BEC leaves behavioral clues
• Inbox rules and logins are key indicators
• Always confirm urgent changes with a call
• Build a checklist and practice response

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Scams are no longer simple email tricks, they are multi-layered social engineering attacks designed to exploit urgency, trust, and emotion. In this consolidated guide, we’ve shown how BEC evolves across invoices, vendors, and payroll, and how small actions — like verification and dual approval — can stop them cold.