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Detection Strategies DET0503 — Behavioral Detection Strategy for Exfiltration Over Symmetric Encrypted Non-C2 Protocol
DET0503

Behavioral Detection Strategy for Exfiltration Over Symmetric Encrypted Non-C2 Protocol

4 analytic(s) · 1 technique(s) detected

Analytics

4
AN1389 Analytic 1389
Windows

Detects the execution of non-browser processes establishing outbound encrypted network connections using uncommon symmetric encryption protocols (e.g., AES via PowerShell or custom scripts) to alternate external destinations.

WinEventLog:Sysmon EventCode=3, 22 WinEventLog:Sysmon EventCode=1
[PayloadEntropyThreshold] Flag high-entropy payloads sent over unexpected protocols.
[TimeWindow] Define allowable transfer window (e.g., abnormal traffic outside business hours).
[ExecutableAllowlist] List of known-good binaries for encrypted traffic (e.g., Chrome, Outlook).
AN1390 Analytic 1390
Linux

Detects command-line utilities or scripts using encryption libraries or symmetric algorithms (e.g., OpenSSL AES, GPG, Python + PyCrypto) in conjunction with outbound file transfers or traffic to external destinations.

auditd:SYSCALL execve auditd:SYSCALL connect NSM:Flow conn.log or flow data NSM:Flow ssl.log (for TLS handshake analysis), dns.log (tunneling indicators)
[FileTransferIndicator] Threshold for transferred data size or extension type.
[LibraryCallTracking] Hooks into use of encryption libraries like `libcrypto.so`, `pycrypto`, `gpg`.
AN1391 Analytic 1391
macOS

Detects symmetric key-based encryption operations (e.g., AES via Python, AppleScript, or OpenSSL) followed by unusual outbound connections from non-browser applications or scripted tools.

macos:unifiedlog log stream process subsystem macos:osquery socket_events macos:unifiedlog log stream network activity
[ApplicationProfileBaseline] Expected outbound connection profiles per app.
[EncryptionRoutinePattern] Indicators of manual encryption operations (e.g., script strings invoking AES).
AN1392 Analytic 1392
ESXi

Detects unexpected encrypted egress traffic from management services (e.g., hostd) or guest VMs utilizing symmetric encryption without traditional protocols (e.g., FTP with embedded AES ciphertext).

esxi:vmkernel egress log analysis esxi:hostd execution + payload hints NSM:Flow host switch egress data
[GuestVMExfilWatchlist] VMs with data sensitivity labels or outside normal behavior.
[ServiceEgressProfile] Expected egress destinations and volume for core services.

Details

MITRE ID
DET0503
STIX ID
x-mitre-detection-strategy--5d368ccf-2946-4a01-bfae-c18064b6187a
Analytics
4
Techniques Detected
1
By Tactic
Exfiltration
1
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