Using Incident Response (IR) for Threat Investigation

Incident Response (IR) is not just about containing and eradicating threats it also plays a critical role in providing threat context, validating detections, and enriching ongoing investigations. In a modern setup with NDR and Threat Intelligence, incident response (IR) bridges raw alerts and actionable insights.

Why Use Incident Response for Threat Context?

When NDR detects an anomaly (e.g., lateral movement, unusual DNS traffic), Incident Response teams validate and investigate:

IR Cycle Integrated with NDR

1. Detection (NDR)

   • Behavior-based anomaly

   • TI-enriched alert (e.g., known bad IP)

2. Triage (IR/SOC)

   • Review context (user, device, location, frequency)

   • Correlate with endpoint logs, SIEM, threat feeds

3. Investigation

   • Timeline reconstruction (who/what/when/how)

   • Forensic analysis (PCAPs, logs, memory, disk images)

4. Containment

   • Block communication (firewall, NAC)

   • Isolate device/user

5. Eradication & Recovery

   • Remove malware or persistence mechanisms

   • Restore systems, change credentials

6. Lessons Learned / Threat Hunting

   • Feed new indicators back into NDR/TI/SIEM

   • Build proactive detection rules (YARA, Suricata, Sigma)

Tools That Help IR Teams Use NDR Data

What IR Adds to Threat Context

1. Attribution

• Based on TTPs, malware samples, TI matches, and adversary behaviors (MITRE ATT&CK).

• Helps determine if its opportunistic malware, an APT, insider threat, etc.

2. Scope

• How many systems/users affected?

• When did it start?

• Was data exfiltrated?

3. Root Cause

• How did the attacker get in?

• Was it phishing, unpatched vulnerability, weak credentials?

• Was there a proactive incident response services in place?

Real-World Example

Detection: NDR detects abnormal DNS requests to a dynamic DNS domain.

Without IR:

• Alert may be ignored if the analyst doesnt see immediate context.

With IR:

• Analyst finds that domain is used by PlugX malware (via TI).

• Memory analysis reveals DLL injection.

• Network forensics show C2 behavior every 2 minutes (beaconing).

• Containment is triggered, new IOC is added to NDR and SIEM.

Best Practices

• Run tabletop exercises with NDR + incident response scenarios.

• Use IR findings to tune behavioral models in NDR.

• Ensure incident reports feed into threat intelligence.

• Maintain a playbook library (SOAR-driven if possible).

• Automate IOC enrichment (Cortex, VirusTotal, OTX) during IR.

Key Steps: Threat Investigation in IR

1. Initial Triage

• Review the alert (from NDR, SIEM, EDR, user report, etc.)

• Correlate with other data sources: logs, flow data, DNS queries, endpoint telemetry

• Determine severity, scope, and potential impact

2. Scoping the Incident

• Identify all compromised assets (IP addresses, users, devices)

• Establish a timeline of events (initial access ? privilege escalation ? lateral movement ? exfiltration)

3. Data Collection

• Network logs

• Packet captures

• Endpoint logs

• Authentication logs

• File system and memory images (if needed)

4. Forensic Analysis

• Analyze suspicious processes, binaries, network connections

• Reconstruct attacker behavior (e.g., use of PSExec, PowerShell, C2 traffic)

• Map activity to known TTPs (MITRE ATT&CK framework)

5. Threat Attribution (Optional)

• Determine if the attack maps to a known threat group

• Leverage threat intelligence for context (actor behavior, known malware, infrastructure)

Here is an example scenario where there is an NDR alert beaconing to a suspicious external IP every 60 seconds. Theincident response team action would be:

1. Validate Alert

   • PCAP shows HTTP over port 443 (unusual behavior).

   • Domain in request matches a known threat actor's infrastructure.

2. Expand Scope

   • Endpoint logs show PowerShell script execution.

   • Lateral connections from that host to others over SMB.

3. Contain & Investigate

   • Isolate host.

   • Pull memory image.

   • Discover persistence via scheduled task and DLL sideloading.

4. Attribution & Enrichment

   • Matches known PlugX malware behavior.

   • IOC added to NDR and EDR platforms.

5. Documentation & Learning

   • Write report, feed back indicators to detection systems.

   • Adjust firewall/NDR rules to detect similar activity in future.