Hunting For Unusual Network Connections
When to Use
- When proactively hunting for indicators of hunting for unusual network connections in the environment
- After threat intelligence indicates active campaigns using these techniques
- During incident response to scope compromise related to these techniques
- When EDR or SIEM alerts trigger on related indicators
- During periodic security assessments and purple team exercises
Prerequisites
- EDR platform with process and network telemetry (CrowdStrike, MDE, SentinelOne)
- SIEM with relevant log data ingested (Splunk, Elastic, Sentinel)
- Sysmon deployed with comprehensive configuration
- Windows Security Event Log forwarding enabled
- Threat intelligence feeds for IOC correlation
Workflow
- Formulate Hypothesis: Define a testable hypothesis based on threat intelligence or ATT&CK gap analysis.
- Identify Data Sources: Determine which logs and telemetry are needed to validate or refute the hypothesis.
- Execute Queries: Run detection queries against SIEM and EDR platforms to collect relevant events.
- Analyze Results: Examine query results for anomalies, correlating across multiple data sources.
- Validate Findings: Distinguish true positives from false positives through contextual analysis.
- Correlate Activity: Link findings to broader attack chains and threat actor TTPs.
- Document and Report: Record findings, update detection rules, and recommend response actions.
Key Concepts
| Concept |
Description |
| T1071 |
Application Layer Protocol |
| T1095 |
Non-Application Layer Protocol |
| T1571 |
Non-Standard Port |
Tools & Systems
| Tool |
Purpose |
| CrowdStrike Falcon |
EDR telemetry and threat detection |
| Microsoft Defender for Endpoint |
Advanced hunting with KQL |
| Splunk Enterprise |
SIEM log analysis with SPL queries |
| Elastic Security |
Detection rules and investigation timeline |
| Sysmon |
Detailed Windows event monitoring |
| Velociraptor |
Endpoint artifact collection and hunting |
| Sigma Rules |
Cross-platform detection rule format |
Common Scenarios
- Scenario 1: Backdoor communicating to C2 on non-standard port
- Scenario 2: Data exfiltration over DNS to attacker nameserver
- Scenario 3: Compromised host scanning internal network
- Scenario 4: Cryptominer connecting to mining pool
Output Format
Hunt ID: TH-HUNTIN-[DATE]-[SEQ]
Technique: T1071
Host: [Hostname]
User: [Account context]
Evidence: [Log entries, process trees, network data]
Risk Level: [Critical/High/Medium/Low]
Confidence: [High/Medium/Low]
Recommended Action: [Containment, investigation, monitoring]
---
name: hunting-for-unusual-network-connections
description: Hunt for unusual network connections by analyzing outbound traffic patterns, rare destinations, non-standard ports, and anomalous connection frequencies from endpoints.
license: Apache-2.0
---
# Hunting For Unusual Network Connections
## When to Use
- When proactively hunting for indicators of hunting for unusual network connections in the environment
- After threat intelligence indicates active campaigns using these techniques
- During incident response to scope compromise related to these techniques
- When EDR or SIEM alerts trigger on related indicators
- During periodic security assessments and purple team exercises
## Prerequisites
- EDR platform with process and network telemetry (CrowdStrike, MDE, SentinelOne)
- SIEM with relevant log data ingested (Splunk, Elastic, Sentinel)
- Sysmon deployed with comprehensive configuration
- Windows Security Event Log forwarding enabled
- Threat intelligence feeds for IOC correlation
## Workflow
1. **Formulate Hypothesis**: Define a testable hypothesis based on threat intelligence or ATT&CK gap analysis.
2. **Identify Data Sources**: Determine which logs and telemetry are needed to validate or refute the hypothesis.
3. **Execute Queries**: Run detection queries against SIEM and EDR platforms to collect relevant events.
4. **Analyze Results**: Examine query results for anomalies, correlating across multiple data sources.
5. **Validate Findings**: Distinguish true positives from false positives through contextual analysis.
6. **Correlate Activity**: Link findings to broader attack chains and threat actor TTPs.
7. **Document and Report**: Record findings, update detection rules, and recommend response actions.
## Key Concepts
| Concept | Description |
|---------|-------------|
| T1071 | Application Layer Protocol |
| T1095 | Non-Application Layer Protocol |
| T1571 | Non-Standard Port |
## Tools & Systems
| Tool | Purpose |
|------|---------|
| CrowdStrike Falcon | EDR telemetry and threat detection |
| Microsoft Defender for Endpoint | Advanced hunting with KQL |
| Splunk Enterprise | SIEM log analysis with SPL queries |
| Elastic Security | Detection rules and investigation timeline |
| Sysmon | Detailed Windows event monitoring |
| Velociraptor | Endpoint artifact collection and hunting |
| Sigma Rules | Cross-platform detection rule format |
## Common Scenarios
1. **Scenario 1**: Backdoor communicating to C2 on non-standard port
2. **Scenario 2**: Data exfiltration over DNS to attacker nameserver
3. **Scenario 3**: Compromised host scanning internal network
4. **Scenario 4**: Cryptominer connecting to mining pool
## Output Format
```
Hunt ID: TH-HUNTIN-[DATE]-[SEQ]
Technique: T1071
Host: [Hostname]
User: [Account context]
Evidence: [Log entries, process trees, network data]
Risk Level: [Critical/High/Medium/Low]
Confidence: [High/Medium/Low]
Recommended Action: [Containment, investigation, monitoring]
```
