Case Study: Suspicious email meeting invite to an outdated distribution list

On December 15 at 10:07 a.m., our team was alerted to a suspicious email sent to a client of ours from a vendor they hadn't used in a while, but it was not unfamiliar. The message contained a malicious link designed to prompt the recipient to enter their login credentials an all too common tactic used in phishing attempts.

After the email was opened, it triggered an automated response that generated a meeting invitation. This invite was unintentionally sent to several users through an outdated distribution list. Soon after, multiple recipients flagged the meeting invite as suspicious, allowing us to quickly identify the scope of the issue.

Immediate Actions Taken

Protecting the Client and its users was our top priority. We responded immediately by:

• Blocking the sender’s email address and associated domain

• Tracing and removing all related emails from affected inboxes

• Deleting the outdated distribution list, which was no longer in use

  
  

Staying Vigilant

This incident underscores the importance of maintaining up to date distribution lists and remaining vigilant when it comes to unexpected emails or links. Prompt reporting by our users played a critical role in minimizing impact, and swift action by our team ensured the threat was contained. Doing a review a couple times a quarter will help this type of scenario from unfolding in the future to someone else on your team.