Webapp Hunting For Unusual Network Connections

---
name: webapp-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.
domain: webapp
category: threat-intelligence
hide: true
license: Apache-2.0
metadata:
  manifest_entry: src/corpus/webapp-hunting-for-unusual-network-connections/SKILL.md
---
# 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

## Detection Gaps & Validation

- **Beaconing blends in:** low-and-slow C2 with jitter, domain-fronting (SNI/Host mismatch), and HTTPS-on-443 evade port-based rules — JA3/JA3S hashing and rare-destination scoring beat them; non-standard port (T1571) is only the loudest variant.
- **DNS tunneling (T1071.004):** needs query-length/entropy analysis and high TXT/NXDOMAIN volume — connection logs alone won't show it.
- **Telemetry sampling:** Sysmon EID 3 (NetworkConnect) is often throttled or disabled for performance, so short-lived connections are missed — pair with firewall/Zeek `conn` logs for ground truth.
- **Lost attribution:** when C2 runs inside an injected/legit process (svchost.exe), EID 3 names the wrong owner — correlate with EID 1/EID 8 to find the real source.
- **Validate:** simulate beaconing (benign curl loop or a C2 emulator) to a rare host; confirm EID 3 + proxy logs both capture it.
- **FP tuning:** baseline cloud/CDN/telemetry and software-update destinations per process, not per host.

## 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]
```