HC3 TLP Clear- Sector Alert: Defense and Mitigations from E-mail Bombing – March 12, 2024

Overview 

E-mail bombing, also known as mail bomb or letter bomb attacks, occur when a botnet (a single actor or group of actors) flood an e-mail address or server with hundreds to thousands of e-mail messages. They are a type of Denial of Service (DoS) attack that allows attackers to bury legitimate transaction and security messages in an unsuspecting inbox by rendering the victim’s mailbox useless. By overloading a victim’s inbox, attackers hope that a victim will miss important e-mails like account sign-in attempts, updates to contact information, financial transaction details, or online order confirmations. 

This type of attack is of particular importance to the Healthcare and Public Health (HPH) sector. In 2016, unknown assailants launched a massive cyber attack aimed at flooding thousands of targeted “dot-gov” (.gov) e-mail inboxes with subscription requests, rendering many unusable for days. E-mail bombs are not only an inconvenience to the victim, but to everyone using that particular server. When an e-mail server is impacted by a DDoS, it can downgrade network performance and potentially lead to direct business downtime. This Sector Alert provides an overview of types of e-mail bomb techniques, as well as defenses and mitigations for targets of this type of attack.

View the detialed report below.