Investigating a Compromised Email Account

Question

An email account belonging to a company manager is suspected to have been hacked, resulting in unauthorized emails being sent to customers on her behalf. Despite having taken several security measures—changing the password, using Bitdefender AV, enabling MFA, and having Microsoft Defender—questions remain about how the account was compromised.

The following steps have been taken so far:

• Checked the message trace and found the unauthorized email in the "Sent Items."
• Reviewed the Get-CompromisedUserDetailReport PowerShell documentation.
• Consulted the Office 365 Defender guidelines for responding to a compromised email account.

The client is requesting a root cause analysis detailing how the compromise occurred, as well as recommendations for additional security measures to prevent future incidents.

Answer 1

Hello @Mohana Reddy
I understand that a company manager's email account is suspected to have been hacked, leading to unauthorized emails being sent to customers on her behalf. Despite implementing several security measures having Microsoft Defender, there are still questions regarding how the account was compromised. Although some steps have been taken to secure the account, the client is now requesting a root cause analysis to determine how the compromise occurred.

The root cause of the account compromise may be a password spray attack, a growing threat where attackers try to access multiple accounts using a few common passwords. Unlike brute force attacks that target one account with many password attempts, password spray attacks target several accounts with limited password combinations. This method is particularly effective against organizations with weak or easily guessable passwords, leading to significant data breaches and financial losses. Attackers often use automated tools or abuse legitimate cloud services, such as virtual machines or containers, to carry out these attacks.

for additional information regarding the safety measures to your identity infrastructure follow the document: https://learn.microsoft.com/en-us/azure/security/fundamentals/steps-secure-identity

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