Legitimate Senders, Weaponized: How Abnormal Stops Email Bombing Attacks

Email bombing is a targeted attack method in which malicious actors abuse legitimate services, like newsletters and subscription forms, to flood users’ inboxes. These messages slip past traditional filters precisely because they arrive from trusted sources, but their volume alone is enough to paralyze productivity and obscure the signals that matter most.

As the noise piles up, employees miss critical alerts, lose track of legitimate requests, and waste valuable time sorting through low-priority clutter—all while attackers exploit the confusion to launch follow-up attacks.

Malicious actors use scripts, botnets, and public APIs to subscribe victims to hundreds or thousands of legitimate email lists. The goal is to distract the target and mask more malicious activity beneath the inbox avalanche.

Why it’s effective:

• Messages bypass spam filters because they come from trusted senders.

• Manual triage wastes valuable hours.

• Critical communications get buried.
  

Beneath the surface-level disruption, email bombing creates the perfect conditions for more targeted, high-impact attacks to succeed.

Email bombing isn’t just disruptive—it’s strategic.

Taking advantage of the noise, attackers follow up by impersonating IT or security staff, contacting employees under the guise of “resolving the issue.”

Attackers then guide their targets to:

• Install remote access tools like TeamViewer, Anydesk, or Microsoft Quick Assist.

• Grant system access or run PowerShell scripts.

• Respond to malicious follow-up emails buried within the influx.

Attackers use these tactics to:

• Mask fraudulent activities, such as unauthorized withdrawals or account takeovers.

• Gather reconnaissance data—such as IP addresses, ISPs, and system behaviors—by monitoring how users interact with malicious messages.

• Deploy secondary attacks, including ransomware or phishing campaigns, using the access gained from manipulated employees​.

Email bombing takes advantage of a fundamental blind spot in legacy email security.

Because these messages come from legitimate sources and don’t contain malicious payloads, they’re rarely flagged or quarantined. But while each message may appear harmless on its own, the attack lies in the volume and the distraction it creates—making it easy for attackers to conceal phishing attempts, account alerts, or follow-up exploits.

This is where behavior-based security becomes essential.

Abnormal takes a behavioral approach that models normal communication patterns for every user and organization.

By building a historical baseline of typical mailbox activity, Abnormal detects unusual spikes in inbound volume—an early signal of a spam bomb in progress. Velocity-based detectors identify sudden influxes of messages from disparate senders, even when each email appears harmless on its own.

Once the attack is identified, Abnormal acts immediately. The platform removes spam bombing messages from inboxes in real time, cutting through the clutter and stopping potential social engineering campaigns before they begin.

At the same time, Abnormal performs retroactive analysis, reviewing the prior 24 hours of email activity to identify and remove additional messages tied to the campaign—ensuring even delayed or distributed attacks are fully contained. This layered approach helps security teams stay ahead of subtle threats, restore visibility, and protect users from the chaos email bombing creates.

In this anonymized, real-world example, a typical week for this user saw Abnormal remediate seven spam messages.

But during a targeted email bombing attack on the same user, Abnormal detected the surge and remediated over 1,000 messages in just 20 minutes—all from legitimate sources.

The swift response kept the employee focused on their work, while preventing the kind of confusion attackers exploit for phishing and BEC breaches.

Email bombing isn’t just a nuisance—it’s a modern gateway to social engineering and a serious threat to enterprise security. Abnormal helps organizations restore inbox visibility, eliminate confusion, and prevent the follow-up attacks that often hide in plain sight. By modeling normal communication behavior, our platform detects and stops these threats before they escalate, keeping your workforce focused, protected, and secure.

See how Abnormal stops email bombing and targeted email threats with behavioral AI built to protect your workforce. Schedule a demo today.