The “Bid Invitation” Email Scam Is Back — How Business Email Compromise Is Hitting Littleton and Denver Area Businesses

“Good afternoon,
Here is the bid invitation.
Please review and let me know what you think.
Document password: 233233.”

At first glance, this email looks harmless. Professional. Routine. Something many businesses in Denver and Littleton see every week.

In reality, this is one of the most common entry points for business email compromise (BEC) attacks currently affecting Denver small businesses, especially those using Microsoft 365 or Google Workspace.

What makes this scam particularly dangerous is that it often comes from a real business email account that has already been compromised.

What Is Business Email Compromise?

Business email compromise is a cyberattack where criminals gain access to a legitimate business email account and use it to:

• steal login credentials,

• monitor conversations,

• redirect payments,

• spread malware, or

• trick vendors and clients into trusting malicious emails.

Unlike obvious spam, BEC attacks look legitimate because they are sent from real inboxes.

This is why business email compromise is now one of the most financially damaging cyber threats to small and mid-sized businesses in Colorado.

Why “Bid Invitation” Emails Are So Effective

Attackers rely on three things:

1. Familiar business language

Phrases like:

• “bid invitation”

• “proposal”

• “RFP”

• “please review”

are common in construction, professional services, engineering, accounting, and trades — all major industries in the Denver metro area.

2. A false sense of security

Including a document password makes the email feel confidential and safe, even though it’s often a red flag.

3. Trust in the sender

Because these messages frequently come from a real, compromised email account, traditional spam filters and human instincts often fail.

How the Attack Actually Works (Step-by-Step)

Step 1: A real mailbox is compromised

This usually happens through:

• fake Microsoft 365 or Google login pages,

• MFA fatigue (push notification abuse),

• weak or optional multi-factor authentication,

• stolen session tokens.

Step 2: The attacker hides inside email

They quietly add:

• inbox rules that delete replies or warnings,

• external forwarding to an attacker-controlled address.

The legitimate user may not notice anything wrong.

Step 3: The “bid invitation” is sent

Short, vague emails are sent to:

• vendors,

• customers,

• internal staff,

• professional contacts.

Step 4: The next victim clicks

The “document” is usually:

• a fake Microsoft or Google document preview that steals credentials, or

• a password-protected attachment designed to bypass email scanning and deliver malware.

From there, the attack spreads.

Why Password-Protected Attachments Are a Warning Sign

In legitimate workflows, password-protected documents are shared securely and intentionally.

In BEC campaigns, passwords are used to:

• lower suspicion,

• bypass automated scanning,

• encourage quick action.

A password does not make a document safe.
In many cases, it does the opposite.

Signs Your Business Email May Already Be Compromised

Many Denver businesses discover BEC after damage has already occurred. Common warning signs include:

• Login alerts from unfamiliar locations

• Emails marked as read that no one opened

• Missing messages or replies

• Unexpected inbox rules or forwarding

• Vendors asking about emails you never sent

• MFA prompts you didn’t request

How to Prevent Business Email Compromise in Denver Businesses

Effective email security is layered. Here’s what actually matters:

1. Monitor risky sign-ins

Review login activity for:

• unusual locations,

• unfamiliar devices,

• impossible travel scenarios.

2. Lock down inbox rules and forwarding

External forwarding and hidden rules are a top persistence method for attackers.

3. Strengthen MFA

SMS-based MFA and optional enforcement are no longer sufficient. Phishing-resistant MFA dramatically reduces risk.

4. Fix email authentication (SPF, DKIM, DMARC)

Missing or misconfigured email authentication allows attackers to impersonate your domain and bypass trust controls.

5. Ensure endpoint protection

If malware is opened, endpoint detection and response (EDR) is often the only thing that stops ransomware or lateral movement.

A Simple Email Security Checklist for Denver Small Businesses

Most businesses we review already have at least one hidden risk, even if they’ve never had a breach.

That’s why we offer a 15-Minute Email Compromise Risk Check, covering:

• risky sign-ins,

• inbox forwarding and rules,

• MFA weaknesses,

• SPF, DKIM, and DMARC configuration,

• endpoint coverage.

You get:

• clear findings,

• plain-English explanations,

• prioritized recommendations.

No scare tactics. No jargon.

Protect Your Business Before the Next Email Click

Business email compromise doesn’t start with ransomware.
It starts with one email that looks safe.

If your business operates in Denver, Littleton, or the surrounding metro area, now is the right time to verify your email security posture. No jargon. No scare tactics.

👉 [Schedule Your Email Security Review]