Email bombing is a disruptive tactic in which a threat actor deliberately floods a victim’s inbox with thousands of unsolicited or automated messages in a short period of time. Discovering your inbox under an email bombing attack requires fast, deliberate action. Threat actors use email bombing as a tool for disruption and facilitation of further attacks. By flooding a target’s inbox with thousands of irrelevant or spam emails, they create a Denial-of-Service (DoS)-like effect on the victim’s email system, making it difficult or impossible to access legitimate communications. This disruption can paralyze an organization’s workflow, delay critical responses, and overload email servers, mimicking the impact of traditional DoS attacks in a digital communication context. Email bombing also serves to divert attention from simultaneous malicious activities, such as phishing emails, malware attachments, or credential theft attempts, by burying these threats in the flood of irrelevant messages.
The reason behind an email bombing attack shapes how you should respond. Attackers typically want one of two things: they’re either planning to demand payment to stop the flood, or they’re trying to bury important alerts while they break into your accounts. This means while you’re dealing with the email chaos, you need to watch your bank accounts, credit cards, and other critical services. Keep monitoring your account closely even after the initial attack subsides. These incidents sometimes come in waves, and staying vigilant helps prevent any follow-up attempts from succeeding. Threat intelligence reveals how Storm-1811 and Black Basta use email bombing in their campaigns. Storm-1811 orchestrates inbox saturation attacks as groundwork for impersonating technical support personnel. During periods of email disruption, they initiate contact by phone or via Microsoft Teams, persuading targets to grant system access via remote tools such as Quick Assist and AnyDesk. Following successful infiltration, Storm-1811 deploys several malware variants, including QakBot, Cobalt Strike, Zbot, and DarkGate, to extract credentials and establish persistent network access. Black Basta employs email bombing differently, using message floods to mask their ransomware deployment activities. Their sophisticated approach incorporates proprietary tools like KNOTWRAP and DAWNCRY for network traversal and data exfiltration prior to encryption. This infrastructure enables rapid compromise of enterprise environments while screening their ransomware operations behind waves of malicious emails. These different techniques require that organizations implement layered defenses addressing both social engineering and technical exploitation vectors.
These floods of messages often mask deeper security threats, so securing your account comes first. Enable multi-factor authentication even if you already use a strong password; attackers sometimes delete security alerts hiding in the avalanche of emails. Securing your account means changing your password immediately. Pick something strong that you’ve never used before. While you’re in your account settings, examine recent logins for unfamiliar devices or locations. Pay special attention to email forwarding rules; savvy attackers often create hidden forwards to monitor compromised accounts.
Managing the flood comes next. Your email provider likely offers filtering tools, including the ability to create a custom rule that automatically moves, copies, or deletes emails based on specific keywords. We recommend creating rules that sort suspected attack emails into a separate folder, keeping your main inbox functional. If the bombardment proves especially aggressive, consider a temporary whitelist strategy. This ensures messages from known contacts still reach you while blocking the attack emails. For critical communications, set up a separate email address and share it only with essential contacts.
Document everything and report the attack to your email provider. They’ve seen this before and often have tools to help block these campaigns at their source. As you work through these steps, stay alert for any signs of account compromise. An email bombing attack might just be smoke, hiding attempts at deeper access to your account or other linked services.
Email bombing should be treated as a high-confidence warning sign, not a minor inconvenience. These attacks are frequently designed to create distraction, suppress visibility, and enable deeper compromise across an environment. A successful response requires addressing both the immediate disruption and the underlying security risks by securing accounts, monitoring for secondary activity, and strengthening defenses against social engineering and malware deployment. Organizations that recognize email bombing as part of a broader attack chain, and respond accordingly, are far better positioned to limit impact and prevent escalation.
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