Mail Protocols
Where this stands
One published detection covers this technique. Every one is unverified — no rule on Siemphony has been executed against real telemetry.
What the technique is
Adversaries may communicate using application layer protocols associated with electronic mail delivery to avoid detection/network filtering by blending in with existing traffic. Commands to the remote system, and often the results of those commands, will be embedded within the protocol traffic between the client and server. Protocols such as SMTP/S, POP3/S, and IMAP that carry electronic mail may be very common in environments. Packets produced from these protocols may have many fields and headers in which data can be concealed. Data could also be concealed within the email messages themselves. An adversary may abuse these protocols to communicate with systems under their control within a victim network while also mimicking normal, expected traffic.
Read it on attack.mitre.orgWhat MITRE says you would watch
- AN0379
Detects unauthorized use of SMTP/IMAP/POP3 by suspicious binaries (e.g., PowerShell, rundll32) to exfiltrate data or beacon via email, often bypassing proxy or content filters.
- AN0380
Detects non-interactive or script-driven email transmission using tools like sendmail, mailx, or custom SMTP scripts by background processes, especially when sending attachments or large payloads.
- AN0381
Detects email-sending behavior via Terminal, AppleScript, or Automator that interfaces with SMTP or IMAP, typically using curl or mail-related APIs in unsanctioned contexts.
Technique names and descriptions © MITRE ATT&CK®, CC BY 4.0. Not endorsed by MITRE.