Suspicious SMTP Submission Connection From Non-Mail Process

ATT&CK techniques

C2

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1071.001Web Protocols
Exfiltration
Impact

What it detects

This rule detects an outbound connection to TCP port 587 (SMTP submission) initiated by a process that is not a known mail client. This behavior matches .NET infostealers such as Agent Tesla and XLoader that were hidden in bitmap resources and exfiltrate stolen credentials directly over SMTP. Direct SMTP use by arbitrary binaries is a strong data-theft indicator.

Reporting behind it

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Suspicious SMTP Submission Connection From Non-Mail Process

Pivot detection · T1071.001 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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