Detection Strategy for Non-Standard Ports

Technique Detected:  Non-Standard Port | T1571

ID: DET0227
Domains: Enterprise
Analytics: AN0633, AN0634, AN0635, AN0636
Version: 1.0
Created: 21 October 2025
Last Modified: 21 October 2025

Analytics

AN0633

Processes initiating outbound connections on uncommon ports or using protocols inconsistent with the assigned port. Correlating process creation with subsequent network connections reveals anomalies such as svchost.exe or Office applications using high, atypical ports.

Log Sources
Data Component Name Channel
Network Connection Creation (DC0082) WinEventLog:Security EventCode=5156
Process Creation (DC0032) WinEventLog:Sysmon EventCode=1
Mutable Elements
Field Description
PortThresholds Define what constitutes a 'non-standard port' based on organizational baselines (e.g., allow 443/80/22 but flag 8088/587/3389 changes).
ProcessAllowList Processes normally allowed to use non-standard ports (e.g., custom apps).
TimeWindow Correlate process creation and network activity within N seconds.

AN0634

Unusual daemons or user processes binding/listening on ports outside of standard ranges, or initiating client connections using mismatched protocol/port pairings.

Log Sources
Data Component Name Channel
Network Traffic Flow (DC0078) auditd:SYSCALL socket/connect syscalls
Application Log Content (DC0038) linux:syslog processes binding to non-standard ports or sshd configured on unexpected port
Process Creation (DC0032) linux:osquery process listening or connecting on non-standard ports
Mutable Elements
Field Description
AllowedServices Exclude ports intentionally configured for enterprise apps.
PayloadEntropyThreshold Define thresholds for anomalous payload entropy to catch tunneled traffic.

AN0635

Applications making outbound connections on non-standard ports or launchd services bound to ports inconsistent with system baselines.

Log Sources
Data Component Name Channel
Network Traffic Flow (DC0078) macos:unifiedlog outbound TCP/UDP traffic over unexpected port
Process Creation (DC0032) macos:unifiedlog launchd services binding to non-standard ports
Mutable Elements
Field Description
BaselinePortProfiles Define expected macOS service port usage (e.g., AirDrop, Bonjour).

AN0636

VM services or management daemons communicating on ports not defined by VMware defaults, such as vpxa or hostd processes initiating traffic over high-numbered or unexpected ports.

Log Sources
Data Component Name Channel
Network Traffic Flow (DC0078) esxi:vpxd ESXi service connections on unexpected ports
Network Traffic Content (DC0085) esxcli:network listening sockets bound to non-standard ports
Mutable Elements
Field Description
ESXiAllowedPorts Default VMware service ports that should not be flagged.