How We Stopped a Business Email Compromise Before It Became a Major Security Incident

BITS Melbourne detected and contained a business email compromise after a phishing attack attempted to gain access to a Microsoft 365 account, preventing further unauthorised activity.

Cybersecurity threats continue to evolve, and one of the most common attacks targeting businesses today is a Business Email Compromise (BEC).

Recently, BITS Melbourne responded to a security incident where a user unknowingly entered their Microsoft 365 credentials into a phishing website. While situations like this can often lead to significant financial loss, data exposure, or email fraud, early detection and layered security controls helped prevent the incident from escalating.

This case study demonstrates the importance of proactive cybersecurity monitoring and why modern businesses need more than just antivirus software to stay protected.

The Initial Incident

A staff member received what appeared to be a legitimate email.

The email contained a link directing the user to what looked like a Microsoft 365 login page.

Unfortunately, the page was a phishing website designed to steal Microsoft 365 credentials.

Believing the request to be legitimate, the user entered their username and password.

At this point, many businesses would be completely unaware that their credentials had been compromised.

However, within minutes, several security systems began detecting suspicious activity.

The First Warning Sign

Shortly after the credentials were entered, an automated security alert was generated.

The alert detected the creation of a suspicious Microsoft 365 inbox rule.

The rule was configured to:

• Move incoming emails from the Inbox

• Redirect messages into the RSS Feeds folder

• Automatically mark emails as read

This technique is commonly used by attackers to hide communications from business owners and staff while they continue monitoring email conversations in the background.

The behaviour immediately triggered an alert within the client's email security platform.

Automated Protection Activated

One of the most important aspects of this incident was that the suspicious activity was detected automatically.

The security platform immediately:

• Generated a high-priority alert

• Notified BITS Melbourne

• Identified the suspicious inbox rule

• Automatically blocked the affected account

This rapid response significantly reduced the attacker's opportunity to gain further access.

Automated cybersecurity monitoring detected suspicious activity, blocked the affected account, and initiated incident response procedures before the business email compromise could escalate.

Without these automated controls, the compromised account may have remained active for hours or even days before being discovered.

Investigation and Remediation

Once the alert was received, our team immediately began investigating the incident.

The following actions were taken:

Password Reset

The user's Microsoft 365 password was reset immediately to prevent further unauthorised access.

Forced Sign Out

All active Microsoft 365 sessions were revoked, ensuring any existing attacker sessions were terminated.

Inbox Rule Review

All mailbox rules were reviewed and the malicious rule was removed.

Sign In Log Analysis

Microsoft 365 sign-in logs were analysed to identify:

• Suspicious login attempts

• Geographic anomalies

• Additional unauthorised activity

• Evidence of further compromise

Security Verification

Additional checks were performed to confirm:

• No mailbox forwarding had been configured

• No privileged access changes had been made

• No other accounts had been affected

The Outcome

Fortunately, because the incident was detected quickly and responded to immediately:

✅ No financial loss occurred

✅ No sensitive data was accessed

✅ No email conversations were compromised

✅ No additional accounts were affected

✅ The attack was successfully contained

The business was able to continue operating normally with minimal disruption.

Why Business Email Compromise Attacks Are So Dangerous

Business Email Compromise attacks are among the most financially damaging cyber threats facing organisations today.

Attackers commonly use compromised email accounts to:

• Impersonate staff members

• Request fraudulent payments

• Redirect invoices

• Steal sensitive information

• Gain access to additional systems

In many cases, organisations do not realise they have been compromised until significant damage has already occurred.

The Importance of Layered Security

This incident highlights why businesses need multiple layers of protection.

Security is no longer just about antivirus software.

Modern businesses should consider:

• Advanced email filtering

• Endpoint protection

• Multi-factor authentication

• Continuous monitoring

• Security awareness training

• Microsoft 365 security controls

• Automated threat detection

When these layers work together, threats can often be identified and stopped before serious damage occurs.

How BITS Melbourne Helps Protect Businesses

At BITS Melbourne, we help Melbourne businesses improve their cybersecurity posture through proactive monitoring, advanced threat detection, and managed IT services.

Our cybersecurity solutions help identify suspicious activity early, allowing businesses to respond before minor incidents become major security events.

Whether it's phishing protection, Microsoft 365 security, endpoint protection, or proactive monitoring, our goal is simple:

Detect threats early and minimise business risk.

Could Your Business Detect This Attack?

If a staff member entered their Microsoft 365 credentials into a phishing website today, would your business know about it?

Many organisations don't discover these incidents until it's too late.

If you're unsure whether your current security controls would detect and respond to this type of threat, consider booking a free IT assessment with BITS Melbourne.

Call today to learn about our proactive ways we helped with a Business Email Compromise Remediation.