DET0262 Detection Strategy for Dynamic Resolution through DNS Calculation
| Item |
Value |
| ID |
DET0262 |
| Version |
1.0 |
| Created |
21 October 2025 |
| Last Modified |
21 October 2025 |
Technique Detected: T1568.003 (DNS Calculation)
Analytics
Windows
AN0728
Monitor DNS query results where subsequent connections use derived or unusual port numbers not explicitly resolved, especially when tied to suspicious processes. Correlate Sysmon DNS logs (Event ID 22) with process creation and socket activity.
Log Sources
Mutable Elements
| Field |
Description |
| PortDeviationThreshold |
Deviation from common service ports (e.g., >1024 when DNS resolved service expects 80/443) |
| TimeWindow |
Correlation window between DNS response and network connection (e.g., 5 minutes) |
Linux
AN0729
Inspect resolver and audit logs for processes initiating outbound connections to ports calculated from DNS response IPs. Abnormal ephemeral port usage shortly after DNS queries can indicate DNS calculation behavior.
Log Sources
Mutable Elements
| Field |
Description |
| EphemeralPortRange |
Configured ephemeral port ranges per environment to reduce false positives |
| ResolverWhitelist |
Exclude trusted resolvers or internal services from analysis |
macOS
AN0730
Use unified logs to detect unusual DNS responses correlated with subsequent connections to calculated or non-standard ports. Monitor non-browser apps making repeated outbound connections that deviate from expected patterns.
Log Sources
Mutable Elements
| Field |
Description |
| ProcessAllowlist |
Expected processes allowed to open non-standard ports (e.g., developer tools) |
| ConnectionVolumeThreshold |
Volume of unusual connections needed before flagging as suspicious |
ESXi
AN0731
Analyze ESXi syslogs for management agents or VMs making outbound connections to dynamically calculated ports derived from DNS responses. Cross-check with VM traffic baselines to identify anomalies.
Log Sources
Mutable Elements
| Field |
Description |
| ManagementPlaneIPs |
Known trusted ESXi management plane IPs to exclude from alerts |
| DomainReputationFeed |
Integrate external feeds for reputation context on DNS-derived domains |