Email Bombing: The Hidden Threat Behind the Flood of Messages
When Inbox Chaos is Just the Beginning: Defending Against Email Bombing
Email Bombing: The Hidden Threat Behind the Flood of Messages
Understanding the Threat
Email bombing, also known as spam bombing, is a sophisticated cyber attack technique where threat actors flood victims’ inboxes with a large volume of emails in a short period. Recently, security vendor Darktrace published research detailing how these attacks work and the hidden dangers they present.
What is Email Bombing?
Email bombing is a cyberattack where attackers send hundreds or even thousands of emails to targets within a short timeframe—sometimes as little as a few minutes. While this might seem merely annoying, these attacks typically have more sinister goals than just cluttering your inbox.
How Does it Work?
Rather than sending spam directly, attackers typically sign up their targets for multiple email subscription services, flooding inboxes indirectly with subscribed content. This tactic has been observed being used by various threat actors, including ransomware groups like Black Basta (also known as Storm-1811).
What makes these attacks particularly effective is their ability to bypass standard security tools. Since the emails often come from legitimate services and subscription confirmations, they typically appear legitimate to security filters that analyze messages individually rather than identifying unusual patterns in volume.
The Real-World Attack Darktrace Uncovered
In early 2025, Darktrace detected an email bombing attack where a user received over 150 emails from 107 unique domains in under five minutes. Each of these emails successfully bypassed traditional Security Email Gateway (SEG) protections but were detected by Darktrace’s behavioral analysis.
In the campaign detailed by Darktrace, the attackers overloaded victims with these subscription emails only to then send another message posing as IT staff, using the initial email bombing as pretext for offering IT assistance.
Following the email flood, the attackers initiated contact with the victim using Microsoft Teams while impersonating the organization’s IT department. After establishing a false sense of trust and urgency due to the “email problem,” they convinced the user to divulge their credentials using Microsoft’s Quick Access remote management tool.
(Graph Showing the Unusual spike in unusual emails observed by Darktrace EMAIL – Soursce: Darktrace)
The Hidden Danger: Beyond the Inbox
What happened next revealed the true purpose of the attack. Darktrace observed that shortly after the Teams call, the compromised device began scanning and performing reconnaissance activities on the network. The attacker first conducted LDAP reconnaissance of the wider network environment to gather user information, followed by network scanning and multiple attempts to authenticate to other internal systems.
According to Nathaniel Jones, VP of Security and AI at Darktrace, email bombing has multiple malicious purposes: “Attackers use it to distract security teams, overwhelm logging systems, hide malicious emails among benign ones, and trigger rate limiting in security tools.”
(EMAIL’s detection of a large number of unusual emails sent during a short period of time – Soursce: Darktrace)
How to Protect Your Organization
While certain defensive tools can help, mitigating email bombing attacks requires a multi-layered approach focused on defending against the social engineering component. Jones emphasizes that “user training and incident response procedures are essential.”
Employees should be taught to recognize when they’re being manipulated through manufactured problems designed for social engineering. Organizations should develop clear protocols for handling sudden email disruptions and verifying IT support contacts. Creating alternative communication channels for emergencies can provide resilience against these attacks.
According to J Stephen Kowski, Field CTO at SlashNext Email Security+, “These attacks aren’t just about mail—they’re a clever way to flood inboxes with legitimate-looking emails, making it harder to spot the real threats hidden in the chaos.” The key to defending against these attacks is detecting behavioral anomalies rather than relying solely on content-based filters.
How CinchOps Can Help Secure Your Business
At CinchOps, we understand that email security goes beyond simple spam filtering. Our comprehensive email protection system uses advanced behavioral analysis to detect unusual patterns—not just malicious content. We can identify and block email bombing attacks before they overwhelm your employees’ inboxes and lead to broader network compromises.
Our security solutions include:
- Behavioral Email Analysis: We monitor email patterns to detect unusual volumes from multiple sources, even when individual messages appear legitimate.
- Advanced Security Awareness Training: We train your employees to recognize social engineering tactics that often accompany email bombing attacks.
- Multi-factor Authentication: We implement robust authentication systems to prevent credential theft, even if employees are manipulated.
- Network Monitoring: Our solutions detect unusual reconnaissance activities that follow initial compromise, stopping attackers before they can move laterally through your network.
- 24/7 Security Operations: Our expert team continuously monitors for threats and can respond immediately to suspicious activities.
Don’t wait until your business falls victim to these sophisticated attacks. Contact CinchOps today to learn how our comprehensive security solutions can protect your organization from email bombing and other advanced cyber threats.
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Discover more about our enterprise-grade and business protecting cybersecurity services: CinchOps Cybersecurity
Discover related topics: The Evolution of Phishing: Understanding Precision-Validated Credential Theft
For Additional Information on this topic, check out: Email bombing exposed: Darktrace’s email defense in action
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