imap_brute_external_internal
Explanation
This event is triggered by Netography's Fusion Portal when it detects a brute force password guessing attack against an Internet Message Access Protocol (IMAP) mail client access server. This event specifically looks for activity from the Internet toward Internet facing IMAP servers on your network.
What to Look For
If internal IMAP servers are exposed to the Internet, it is very important to implement a strong password policy as two-factor authentication is not natively supported by the protocol. You should also consider enabling available server controls such as: app-specific passwords, auth-failure delays, temporary account locks, or Fail2ban. Check network logs for additional information and review endpoint security to ensure that sensitive information is secure.
If your organization does not need to use IMAP, and your mail server supports a more secure protocol, consider disabling the IMAP protocol or blocking external access of IMAP(s) ports (TCP/143 & TCP/993).
Related MITRE ATT&CK Categories
Updated 2 days ago