Cross-source coverage

T1071.003 / ATT&CK

Application Layer Protocol: Mail Protocols

7 rules across 3 sources.

From MITRE ATT&CK 19.2

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.

Platforms
Linux · macOS · Network Devices · Windows
Telemetry
WinEventLog:SysmonNSM:Flowauditd:SYSCALLmacos:unifiedlogmacos:osquery

How MITRE says to detect it DET0135

Detection of Mail Protocol-Based C2 Activity (SMTP, IMAP, POP3)

Windows Analytic 0379

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.

  • WinEventLog:Sysmon EventCode=3, 22
  • WinEventLog:Sysmon EventCode=1
  • NSM:Flow smtp.log

Linux Analytic 0380

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.

  • auditd:SYSCALL execve
  • NSM:Flow smtp.log, conn.log

macOS Analytic 0381

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.

  • macos:unifiedlog log stream --predicate 'processImagePath CONTAINS "curl" OR "osascript"'
  • macos:osquery socket_events

Network Devices Analytic 0382

Detects hosts transmitting large volumes of SMTP, IMAP, or POP3 traffic to external IPs or relays that aren't associated with the enterprise mail infrastructure.

  • NSM:Flow smtp.log, conn.log

View on attack.mitre.org ↗

elastic/protections-artifacts

3 rules
Detection Severity Format
Service Communication via Mail Protocol Undefined Elastic TOML
Suspicious Communication via Mail Protocol Undefined Elastic TOML
Suspicious Network Connection to Gmail via Nodejs Undefined Elastic TOML

splunk/security_content

3 rules
Detection Severity Format
Windows File Transfer Protocol In Non-Common Process Path Undefined SPL
Windows Mail Protocol In Non-Common Process Path Undefined SPL
Windows Multi hop Proxy TOR Website Query Undefined SPL

elastic/detection-rules

1 rule
Detection Severity Format
SMTP to the Internet on Port 26/TCP Low Elastic TOML

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