Email bombing, also known as a “spam bomb,” has become a favored tool among threat actors seeking to circumvent traditional security measures and pave the way for more insidious cyber attacks.
This malicious tactic involves bombarding a victim’s email inbox with an overwhelming volume of messages, creating a smokescreen that can disguise attempts at phishing or credential theft. By signing up victims to multiple subscription services, attackers trigger a flood of confirmation emails that can easily go unnoticed by standard email security gateways.
One such incident occurred in early 2025, when Darktrace’s security solutions intercepted an email bombing campaign targeting one of their customers. The attack inundated the victim with over 150 emails from 107 different domains in less than five minutes, evading detection by a widely used Security Email Gateway.
The emails, which covered a range of languages and topics related to account registration, were sent through reputable marketing platforms like Mailchimp’s Mandrill, giving them an air of legitimacy. Although individually harmless, the sheer volume of emails created chaos and confusion for the recipient.
Darktrace’s AI-driven /EMAIL tool was able to flag this abnormal activity and could have prevented the emails from reaching the target’s inbox if set to Autonomous Response mode. However, the aftermath of the email bombing revealed a more sinister intent on the part of the attackers.
Following the email onslaught, the threat actors attempted to exploit the victim through a Microsoft Teams call, impersonating the IT department to create a sense of urgency. Overwhelmed by the relentless emails, the victim fell for the ruse and disclosed their credentials during the call.
The attackers then used legitimate tools like Microsoft Quick Access to conduct reconnaissance on the network, laying the groundwork for further exploitation. The compromised device began scanning the network, trying to connect to internal systems and making multiple failed login attempts.
Darktrace’s Cyber AI Analyst identified these actions as part of a coordinated attack, highlighting critical steps such as LDAP reconnaissance and extensive connection attempts over port 445. Had Darktrace’s autonomous response capabilities been fully activated, the attack’s impact could have been significantly minimized by blocking suspicious connections.
This incident serves as a stark reminder of the evolving sophistication of cyber threats and the importance of advanced AI security solutions like Darktrace in detecting and neutralizing such attacks. The convergence of email bombing, social engineering, and insider threats underscores the pressing need for proactive and adaptive security measures to safeguard organizational data and infrastructure.
In conclusion, the prevalence of email bombing highlights the need for organizations to stay vigilant and invest in cutting-edge cybersecurity solutions that can adapt to the ever-changing threat landscape. By leveraging AI-driven technologies like Darktrace, businesses can fortify their defenses against emerging cyber threats and mitigate potential risks before they escalate.