Securing Email Inboxes: Defending Against Malicious Email Rules

Automated email inbox rules, commonly found in email clients, play a crucial role in managing email communication, according to a recent blog by Barracuda. However, these rules can be exploited by attackers who have compromised an account. Attackers use inbox rules to maintain stealth, move data out of the network, avoid security warnings, hide messages, or even impersonate senior executives for financial gain.

Despite advancements in email detection using machine learning, attackers still employ this tactic effectively.

Email-borne attacks are prevalent, with 75% of surveyed companies experiencing email security breaches in 2022. These attacks range from basic phishing to more sophisticated techniques, including the use of malicious email rules.

To create malicious email rules, attackers first need to compromise a target account, often through phishing or stolen credentials. Once in control, they can set rules to forward sensitive emails externally, hide specific inbound emails, or delete them.

This allows attackers to steal information and money, delay detection, or conduct business email compromise (BEC) attacks, convincing recipients that emails are from legitimate sources to defraud organizations.

Malicious email rules are also used in targeted nation-state attacks, including cyber espionage and theft of intellectual property.

Defending against these attacks is challenging. Changing passwords or implementing multifactor authentication alone may not be sufficient, as malicious rules can persist. Effective defenses require a multifaceted approach that combines prevention, detection, and incident response. Prevention involves stopping attackers from compromising accounts, while detection requires monitoring actions within inboxes, including rule creation and email activity.

Automated email rules can be a double-edged sword, offering convenience but also posing a significant security risk. Organizations must be proactive in safeguarding their email systems, employing a comprehensive strategy to mitigate the threat posed by malicious email rules.