Microsoft 365 and Google Workspace have become central platforms for modern organizations. A single business account may provide access not only to email but also to documents, contacts, calendars, cloud storage, collaboration systems, authentication services and sensitive business information.

That makes a Microsoft 365 or Google Workspace identity extremely valuable to cybercriminals.

Microsoft explains that credentials for a Microsoft Entra ID account can provide access to the associated Microsoft 365 mailbox as well as resources such as OneDrive and SharePoint. Google similarly provides administrators with specific procedures for investigating and securing compromised or hijacked Workspace accounts, including revoking sign-in cookies and OAuth tokens.

Attackers therefore frequently use phishing as the entry point into a cloud account. Once access is obtained, the attack may develop into account takeover, internal phishing, information theft or Business Email Compromise (BEC).

Understanding the distinction is important:

Phishing is usually the method used to deceive a victim. BEC is typically a business-fraud operation in which email identity, trust or a compromised account is used to manipulate business processes.

1. Why Are Microsoft 365 and Google Workspace Accounts Targeted by Phishing Attacks?

1.1 One Account Can Unlock Multiple Business Services

Cloud productivity accounts are particularly attractive because organizations often use a single identity across numerous services.

For example, a compromised Microsoft 365 identity might expose:

• Exchange Online email
• OneDrive files
• SharePoint resources
• Teams-related business information
• Contacts
• Calendars
• Organizational directories
• Other applications connected to Microsoft Entra ID

Microsoft specifically warns that after an attacker gains access to an account, the associated mailbox, OneDrive files and SharePoint resources may become accessible.

A compromised Google Workspace account may similarly expose Gmail and other organizational resources available to that particular user.

Therefore, stealing one password can potentially be much more valuable than compromising a standalone email account.

2. Email Accounts Contain Valuable Business Intelligence

A business mailbox can reveal enormous amounts of operational information.

An attacker who gains access may discover:

• Customer names
• Vendor relationships
• Purchase orders
• Quotations
• Invoices
• Bank details
• Payment schedules
• Payroll discussions
• Employee information
• Management conversations
• Contract negotiations
• Password-reset emails
• Meeting schedules
• Travel information
• Financial approvals

This information can subsequently be used to create extremely convincing fraud.

For example, an attacker who discovers an ongoing conversation concerning a ₹5,00,000 vendor payment does not necessarily need to invent a completely new story.

The attacker may attempt to interfere with the existing transaction.

3. Microsoft and Google Login Pages Are Familiar to Users

Millions of employees regularly see Microsoft and Google authentication screens.

Attackers exploit this familiarity.

A phishing email may claim:

Your Microsoft 365 password expires today.

or:

A document has been shared with you through Google Drive.

The victim clicks the link and reaches a website designed to resemble a legitimate login page.

The attacker-controlled page may request:

Email Address → Password → MFA Code

If the victim supplies these details, the attacker may attempt to use them against the genuine service.

The FBI describes phishing as a scheme in which a message appears to come from a legitimate organization and directs the victim to a spoofed website designed to obtain information such as passwords or other sensitive credentials.

4. Cloud Accounts Are Useful for Further Phishing

Compromising one employee can help attackers target other employees.

Consider this scenario:

Step 1: An attacker steals an employee's Microsoft 365 credentials.

Step 2: The attacker signs into the mailbox.

Step 3: The attacker identifies customers and colleagues.

Step 4: Phishing messages are sent from the legitimate compromised mailbox.

Recipients may trust these messages because they originate from an account they already know.

Microsoft notes that attackers commonly use compromised mailboxes to send messages to recipients both inside and outside the victim organization.

This creates an important difference between ordinary spoofing and account takeover.

A spoofed message only pretends to come from someone.

A compromised mailbox can actually be someone's genuine account being controlled by the attacker.

5. Attackers Want Trusted Business Identities

Suppose you receive two messages:

Message A

randomcriminal847@example.com

asks you to pay an invoice.

You will probably be suspicious.

Now consider:

Message B

appears to come from your company's finance manager and references a real supplier and genuine invoice.

That message is much more convincing.

BEC attackers exploit exactly this trust relationship.

The FBI describes BEC as a highly damaging form of online crime in which criminals make messages appear to originate from known and trusted sources while requesting apparently legitimate business actions.

6. Microsoft 365 and Google Workspace Are Often Connected to Financial Workflows

Business email is frequently involved in:

• Purchase approvals
• Vendor payments
• Banking instructions
• Payroll
• Invoice processing
• Tax documents
• Contract approval
• Customer payments
• Wire transfers

Attackers do not necessarily need access to the company's accounting software.

Sometimes they only need to convince the person who does have access.

That is why social engineering remains so effective.

7. Phishing Can Target Passwords, MFA and Sessions

Modern phishing attacks are no longer limited to simple password-stealing pages.

Attackers may target:

• Username and password
• MFA verification codes
• Authentication approvals
• Session cookies
• OAuth permissions
• Recovery information
• Authentication tokens

This is important because MFA significantly improves account security, but organizations should not assume that every form of MFA makes phishing impossible.

Organizations handling sensitive information should increasingly consider phishing-resistant authentication mechanisms such as security keys, passkeys and FIDO2-based authentication where appropriate.

8. OAuth Consent Phishing

An attacker may sometimes avoid asking directly for the victim's password.

Instead, the victim may be encouraged to authorize a malicious application.

The application may request permissions relating to:

• Mail
• Profile information
• Contacts
• Files
• Calendars

A convincing message might say:

"Your administrator has installed a new document management application. Click Accept to continue."

Users should carefully inspect unexpected application-consent requests rather than automatically approving them.

9. What Is Business Email Compromise (BEC)?

Business Email Compromise is a sophisticated form of fraud involving trusted business communications.

The FBI describes BEC/EAC as a scam involving businesses or individuals conducting legitimate transfers of funds, although BEC is not limited exclusively to money transfers; variations can also target personally identifiable information and other valuable information.

The attacker typically impersonates or compromises someone trusted, such as:

• CEO
• Director
• Accountant
• Finance manager
• HR manager
• Vendor
• Customer
• Lawyer
• Business partner

The attacker then attempts to convince another person to perform an action benefiting the criminal.

10. Common BEC Example: CEO Fraud

Suppose an accountant receives:

From: Managing Director
Subject: Urgent Confidential Payment

The message says that an urgent payment must be processed immediately and asks the accountant not to discuss it because the transaction is confidential.

The attacker may use:

• Executive impersonation
• Urgency
• Authority
• Confidentiality
• Fear of delaying an important transaction

The employee processes the payment.

The money goes to an attacker-controlled account.

This is classic BEC.

11. Vendor Invoice Fraud

Another common BEC scenario involves supplier payments.

Imagine that your organization regularly pays:

ABC Technologies Pvt. Ltd.

The attacker learns that an invoice is due.

A message then arrives:

We have changed our bank account. Please make all future payments to the following account.

The invoice may look completely genuine.

The company logo may be correct.

The supplier's contact person's name may be correct.

The invoice number may even correspond with a genuine transaction.

Only the banking information has changed.

The FBI specifically warns about BEC scenarios involving fraudulent changes to payment information and recommends independently verifying changes in account numbers or payment procedures.

12. How Is BEC Different from Phishing?

Although the terms are related, they are not identical.

Feature	Phishing	Business Email Compromise
Primary purpose	Steal credentials, information or deliver malicious content	Manipulate a trusted business process
Typical target	Large numbers of users or selected individuals	Specific employees, executives, vendors or finance personnel
Main technique	Fake messages, links, websites or attachments	Impersonation, compromised accounts and social engineering
Credential theft	Very common	May or may not occur
Malware	Possible	Not required
Payment fraud	Possible	Very common
Research required	Sometimes limited	Frequently extensive
Personalization	Low to very high	Usually high
Compromised mailbox	Not required	Frequently valuable
Main objective	Gain information/access or execute malware	Fraudulent payment, information theft or business manipulation

The most important relationship is:

Phishing can be the first stage of a BEC attack.

13. Example: Phishing Becoming BEC

Consider the complete attack chain.

Stage 1 — Phishing

An accounts employee receives:

Microsoft 365 Security Alert — Your password expires today.

The employee clicks the link.

Stage 2 — Credential Theft

The employee enters credentials into a fake Microsoft login page.

Stage 3 — Account Takeover

The attacker gains access to the employee's cloud account.

Stage 4 — Reconnaissance

Instead of immediately attacking, the criminal studies:

• Inbox
• Sent messages
• Suppliers
• Invoices
• Management structure
• Payment schedules

Stage 5 — Target Selection

The attacker discovers that the company is expecting an invoice from a supplier.

Stage 6 — Fraud

A fraudulent instruction is sent concerning payment details.

Stage 7 — BEC

The finance department transfers money to the attacker's bank account.

Therefore:

Phishing obtained the access. BEC monetized the trust and business relationship.

14. BEC Does Not Always Require Account Hacking

This is extremely important.

A BEC attack can occur without compromising Microsoft 365 or Google Workspace.

Attackers can simply create a similar-looking domain.

Suppose the legitimate domain is:

bisoncompany.com

The attacker might register:

bisoncornpany.com

where letters have been chosen to visually resemble the genuine domain.

Other possibilities include:

bison-company.com

bisoncompany.co

bisoncompanny.com

These are commonly called lookalike domains.

The attacker can then impersonate an employee or vendor.

15. Display Name Spoofing

Attackers may also exploit the display name shown by email applications.

For example:

Display Name: Rajesh Sharma — Managing Director

Actual email:

finance.request@example.net

A user checking only the display name might assume the message is genuine.

Therefore employees should inspect the actual sender address when a message requests:

• Payments
• Passwords
• Bank changes
• Sensitive documents
• Gift cards
• Payroll changes
• Confidential information

16. Email Spoofing and BEC

Email spoofing attempts to make a message appear to originate from another sender or domain.

Microsoft notes that spoofed messages can be used to trick recipients into disclosing credentials, downloading malware or responding with sensitive information, including in BEC scenarios.

Organizations should correctly configure:

SPF — Sender Policy Framework

Identifies mail systems authorized to send mail for a domain.

DKIM — DomainKeys Identified Mail

Cryptographically signs outgoing email so recipients can verify aspects of its authenticity and integrity.

DMARC — Domain-based Message Authentication, Reporting and Conformance

Builds on SPF and DKIM and allows domain owners to specify how receiving systems should handle messages that fail authentication/alignment checks.

SPF, DKIM and DMARC significantly strengthen domain protection, but they do not prevent every BEC technique.

For example, they cannot prevent an attacker from registering a completely separate lookalike domain.

17. Malicious Inbox Rules — A Major Warning Sign

After compromising a mailbox, attackers may create rules that:

• Delete particular emails
• Mark emails as read
• Move messages to hidden folders
• Forward messages
• Hide replies
• Redirect particular communications

Imagine an attacker conducting invoice fraud.

The genuine supplier replies:

We have never changed our bank account.

If the attacker has created a rule that automatically moves messages from that supplier into another folder, the victim might never notice the warning.

Therefore suspicious inbox and forwarding rules should always be investigated during account-compromise response.

18. External Email Forwarding

Attackers may attempt to configure automatic forwarding so that copies of business communications reach an external mailbox.

This can allow continued intelligence collection even after the attacker stops actively checking the mailbox.

Administrators investigating suspected compromise should examine:

• Mailbox forwarding
• Inbox rules
• Delegates
• Connected applications
• OAuth grants
• Sign-in activity
• Recovery information
• Authentication methods

19. Signs of a Microsoft 365 or Google Workspace Account Compromise

Possible indicators include:

• Unexpected password reset
• Unknown MFA registration
• Unrecognized login
• Unexpected authentication prompts
• Emails appearing in Sent Items that the user did not send
• Deleted messages
• New inbox rules
• Unknown forwarding addresses
• Suspicious OAuth applications
• Unusual login locations
• Customers reporting strange emails
• Unexpected password-reset messages
• Changes to recovery information
• New delegates
• Security alerts

Any single indicator may have a legitimate explanation, but combinations should be investigated quickly.

20. How Organizations Can Protect Microsoft 365 and Google Workspace

Enable MFA

Every business account should use multi-factor authentication wherever possible.

The FBI also recommends MFA as part of protection against BEC and phishing-related compromise.

Priority should be given to:

• Administrators
• Directors
• Finance personnel
• HR
• Accounts
• Payroll
• IT administrators

Where supported and practical, use phishing-resistant authentication such as passkeys or hardware security keys for high-risk accounts.

21. Protect Administrator Accounts

Administrator accounts are particularly valuable.

Organizations should avoid using highly privileged administrator identities for routine email and everyday browsing wherever practical.

For example:

user@company.com

may be used for normal work.

A separate privileged account can be reserved for administrative functions.

This reduces exposure of highly privileged credentials.

22. Establish Payment Verification Procedures

Technical controls alone cannot eliminate BEC.

Organizations need business-process controls.

Any request involving:

• New bank details
• Changed bank details
• Large payments
• Urgent wire transfers
• Payroll changes
• Unusual refunds

should require independent verification.

The verification should occur through a trusted channel other than simply replying to the suspicious email.

For example:

Email request → Verify using the supplier's previously known telephone number.

Do not rely on a telephone number supplied inside the suspicious email itself.

The FBI specifically recommends verifying payment requests independently and confirming changes to account numbers or payment procedures.

23. Implement Dual Authorization for Payments

High-value payments should ideally require approval from more than one authorized person.

For example:

Accounts Executive → Finance Manager → Director → Payment

This significantly reduces the chance that one compromised mailbox or one deceived employee can authorize a major fraudulent payment.

24. Train Employees to Recognize BEC Psychology

BEC messages frequently exploit:

Authority

"I am the CEO. Process this immediately."

Urgency

"Payment must be completed within 30 minutes."

Confidentiality

"Do not discuss this transaction with anyone."

Fear

"Our account will be suspended."

Opportunity

"You have received an unexpected refund."

Employees should be trained to recognize these psychological triggers.

25. Configure Microsoft 365 Anti-Phishing Protection

Microsoft 365 organizations should review available protections including:

• Anti-phishing policies
• Anti-spoofing protection
• Impersonation protection where available
• Safe Links where licensed
• Safe Attachments where licensed
• Microsoft Defender alerts
• Authentication policies
• Conditional Access where licensed
• Mailbox auditing
• Sign-in monitoring

Microsoft notes that even with Microsoft 365's anti-phishing capabilities, some phishing messages can still reach mailboxes, making investigation, reporting and proper policy configuration important.

26. Secure Google Workspace Accounts

Google Workspace administrators should similarly review:

• 2-Step Verification
• Security keys/passkeys where appropriate
• Suspicious login alerts
• Gmail security settings
• OAuth application access
• User recovery information
• Email forwarding
• Account activity
• Administrator privileges

If compromise is suspected, Google recommends actions such as suspending the affected account, investigating unauthorized activity, reviewing recovery information and strengthening 2-Step Verification. Suspending an affected Workspace user also resets sign-in cookies and OAuth tokens.

27. What Should You Do After a Suspected BEC Attack?

Speed matters.

Immediately:

1. Contact your IT administrator or security team.
2. Secure the compromised account.
3. Reset affected credentials.
4. Revoke suspicious sessions where appropriate.
5. Review MFA/authentication methods.
6. Investigate inbox and forwarding rules.
7. Review OAuth or connected applications.
8. Check login and audit logs.
9. Search for fraudulent emails sent from the account.
10. Warn affected employees, customers or vendors when necessary.

If money has already been transferred fraudulently, contact the relevant financial institution immediately.

The FBI advises BEC victims to contact their financial institution immediately and request action concerning the institution receiving the fraudulent transfer.

Organizations should also follow applicable local law-enforcement, cybercrime-reporting, insurance, regulatory and data-breach notification requirements.

28. Phishing vs. Account Takeover vs. BEC

These three concepts should not be confused.

Phishing

Objective: Trick the victim.

Example:

Fake Microsoft 365 login page steals credentials.

Account Takeover

Objective: Gain unauthorized control of an account.

Example:

Attacker signs into the employee's Microsoft 365 account using stolen credentials.

Business Email Compromise

Objective: Exploit business trust and processes.

Example:

Attacker uses knowledge or control of business communications to redirect an invoice payment.

The relationship can therefore be:

Phishing → Credential Theft → Account Takeover → Reconnaissance → BEC → Financial/Data Loss

But BEC can also occur without account takeover through spoofing, lookalike domains or executive/vendor impersonation.

29. Why BEC Can Be Harder to Detect Than Traditional Phishing

Traditional phishing often contains something obviously malicious:

• Fake login page
• Suspicious attachment
• Malicious URL

BEC can be much simpler.

For example:

Hi Amit,
Please hold today's payment to ABC Ltd. We have changed our banking arrangements. I'll send the revised account details shortly.

There may be:

• No malware
• No attachment
• No suspicious link
• No request for a password

From a purely technical perspective, the message may look relatively harmless.

The danger lies in the business instruction.

This is why BEC prevention requires cooperation between:

IT + Cybersecurity + Finance + HR + Management + Employees

30. Recommended Business Email Security Model

Organizations using Microsoft 365 or Google Workspace should implement multiple security layers.

Identity Layer

• MFA
• Passkeys/security keys for high-risk users
• Strong authentication policies
• Privileged account separation
• Suspicious login monitoring

Email Layer

• SPF
• DKIM
• DMARC
• Anti-phishing
• Anti-spoofing
• Attachment scanning
• URL protection

User Layer

• Security awareness training
• Phishing simulations
• BEC training
• Verification procedures

Financial Layer

• Dual authorization
• Vendor verification
• Bank-change verification
• Payment thresholds

Monitoring Layer

• Sign-in logs
• Mailbox auditing
• Forwarding-rule monitoring
• OAuth application monitoring
• Security alerts

No single control should be considered sufficient.

Frequently Asked Questions (FAQ)

1. Why do attackers target Microsoft 365 accounts?

Microsoft 365 accounts can provide access to email and, depending on permissions and configuration, resources such as OneDrive and SharePoint. They can also provide attackers with a trusted corporate identity for further attacks.

2. Why do attackers target Google Workspace accounts?

Google Workspace accounts may contain valuable business communications and provide access to organizational cloud services. Compromised accounts can therefore be valuable for information theft, impersonation and further attacks.

3. Is BEC the same as phishing?

No. Phishing is primarily a deception technique used to steal information, credentials or deliver malicious content. BEC focuses on exploiting business trust and communications to cause fraudulent actions.

4. Can phishing lead to BEC?

Yes. Attackers frequently use phishing or spear phishing to obtain credentials or business information that can later facilitate BEC. The FBI specifically identifies spear phishing as one method criminals can use as part of BEC operations.

5. Does BEC require malware?

No. A successful BEC message may contain no malware, attachment or malicious URL.

6. Can BEC occur without hacking an email account?

Yes. Attackers can use spoofing, lookalike domains and impersonation without compromising the genuine mailbox.

7. What is CEO fraud?

CEO fraud is a BEC technique where an attacker impersonates a CEO, director or senior executive to convince employees to make payments, disclose information or perform another sensitive action.

8. What is vendor impersonation?

An attacker pretends to represent a legitimate supplier and requests payment or changes to banking instructions.

9. Can MFA prevent phishing?

MFA significantly improves account security, but organizations should still defend against social engineering, session theft and other advanced attacks. Phishing-resistant authentication provides stronger protection against credential-phishing scenarios.

10. What is a malicious inbox rule?

It is an unauthorized mailbox rule created to hide, delete, redirect, forward or otherwise manipulate messages.

11. What is email spoofing?

Spoofing involves disguising sender information so a message appears to originate from a trusted person or organization.

12. What is a lookalike domain?

It is a domain registered to visually resemble a legitimate company's domain, often by changing, adding or removing characters.

13. Do SPF, DKIM and DMARC stop BEC completely?

No. They are important defenses against domain spoofing but cannot eliminate attacks involving compromised genuine accounts or separately registered lookalike domains.

14. Should employees verify requests to change supplier bank accounts?

Yes. Changes to payment instructions should be independently verified using previously established contact information rather than details supplied in the change request.

15. What should I do if a Microsoft 365 account is compromised?

Secure the account immediately, investigate sign-in activity, review authentication methods, inspect mailbox rules and forwarding, revoke unauthorized access where appropriate, investigate messages sent by the attacker and follow Microsoft's account-compromise response procedures.

16. What should I do if a Google Workspace account is compromised?

Administrators should secure the account, investigate unauthorized activity, review recovery and authentication settings and inspect other suspicious changes. Google provides an administrator checklist specifically for compromised Workspace accounts.

17. Why are finance employees commonly targeted?

They have authority or access relating to invoices, payroll, bank transfers and supplier payments, making them particularly valuable targets for BEC.

18. Can a genuine email address send phishing emails?

Yes. If a legitimate mailbox has been compromised, an attacker may use it to send malicious messages.

19. What is the best protection against BEC?

There is no single solution. Strong authentication, email security, user training, payment-verification procedures, dual authorization and continuous monitoring should work together.

20. What is the most important rule for preventing payment-related BEC?

Never approve an unexpected change to payment or banking instructions solely on the basis of an email. Independently verify the request through a trusted communication channel.

Conclusion

Microsoft 365 and Google Workspace accounts are attractive phishing targets because they sit at the center of modern business communication, identity and cloud collaboration.

A successful phishing attack may give a criminal much more than an email password. Depending on the victim's permissions, it may expose business communications, files, contacts and information about financial processes.

That information can then be weaponized in Business Email Compromise.

The essential distinction is:

Phishing attacks the user to obtain information or access.

Account takeover gives the attacker control of an identity or account.

BEC exploits trust and business processes to obtain money, sensitive information or another fraudulent outcome.

Organizations should therefore treat email security as more than spam filtering. Effective protection requires strong identity security, MFA or phishing-resistant authentication, SPF/DKIM/DMARC, anti-phishing controls, account monitoring, employee education and—critically—independent verification of financial requests.

A technically secure email platform can still be defeated when an employee is persuaded to authorize a fraudulent payment. For that reason, the strongest defense against BEC combines technology, trained people and verified business procedures.

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