Performing Threat Hunting with Elastic SIEM

When to Use

Use this skill when:

• SOC teams need to proactively search for threats not caught by existing detection rules
• Threat intelligence reports describe new TTPs requiring validation against historical data
• Red team exercises reveal detection gaps that need hunting query development
• Periodic hunting cadence requires structured hypothesis-driven investigations

Do not use for real-time alert triage — that belongs in the Elastic Security Alerts queue with automated detection rules.

Prerequisites

• Elastic Security 8.x+ with Security app enabled in Kibana
• Data ingestion via Elastic Agent (Endpoint Security integration) or Beats (Winlogbeat, Filebeat, Packetbeat)
• Data normalized to Elastic Common Schema (ECS) field mappings
• User role with kibana_security_solution and read access to relevant indices
• MITRE ATT&CK framework knowledge for hypothesis generation

Workflow

Step 1: Develop Hunting Hypothesis

Start with a hypothesis based on threat intelligence, ATT&CK technique, or anomaly:

Example Hypothesis: "Attackers are using living-off-the-land binaries (LOLBins) for execution, specifically certutil.exe for file downloads (T1105 — Ingress Tool Transfer)."

Define scope:

• Data sources: logs-endpoint.events.process-*, logs-windows.sysmon_operational-*
• Time range: Last 30 days
• Expected indicators: certutil.exe with -urlcache, -split, or -decode flags

Step 2: Hunt Using KQL in Discover

Open Kibana Discover and query with KQL (Kibana Query Language):

kql
process.name: "certutil.exe" and process.args: ("-urlcache" or "-split" or "-decode" or "-encode" or "-verifyctl")

Refine to exclude known legitimate use:

kql
process.name: "certutil.exe"
  and process.args: ("-urlcache" or "-split" or "-decode")
  and not process.parent.name: ("sccm*.exe" or "ccmexec.exe")
  and not user.name: "SYSTEM"

For PowerShell-based hunting with encoded commands (T1059.001):

kql
process.name: "powershell.exe"
  and process.args: ("-enc" or "-encodedcommand" or "-e " or "frombase64string" or "iex" or "invoke-expression")
  and not process.parent.executable: "C:\\Windows\\System32\\svchost.exe"

Step 3: Use EQL for Sequence Detection

Elastic Event Query Language (EQL) enables hunting for multi-step attack sequences:

Detect parent-child process anomalies (T1055 — Process Injection):

eql
sequence by host.name with maxspan=5m
  [process where event.type == "start" and process.name == "explorer.exe"]
  [process where event.type == "start" and process.parent.name == "explorer.exe"
    and process.name in ("cmd.exe", "powershell.exe", "rundll32.exe", "regsvr32.exe")]

Detect credential dumping sequence (T1003):

eql
sequence by host.name with maxspan=2m
  [process where event.type == "start"
    and process.name in ("procdump.exe", "procdump64.exe", "rundll32.exe", "taskmgr.exe")
    and process.args : "*lsass*"]
  [file where event.type == "creation"
    and file.extension in ("dmp", "dump", "bin")]

Detect lateral movement via PsExec (T1021.002):

eql
sequence by source.ip with maxspan=1m
  [authentication where event.outcome == "success" and winlog.logon.type == "Network"]
  [process where event.type == "start"
    and process.name == "psexesvc.exe"]

Step 4: Investigate with Elastic Security Timeline

Create a Timeline investigation in Elastic Security for collaborative analysis:

1. Navigate to Security > Timelines > Create new timeline
2. Add events from hunting queries using "Add to timeline" from Discover
3. Pin critical events and add investigation notes
4. Use the Timeline query bar for additional filtering:

kql
host.name: "WORKSTATION-042" and event.category: ("process" or "network" or "file")

Add columns for key fields: @timestamp, event.action, process.name, process.args, user.name, source.ip, destination.ip

Step 5: Build Detection Rules from Findings

Convert successful hunting queries into Elastic detection rules:

json
{
  "name": "Certutil Download Activity",
  "description": "Detects certutil.exe used for file download, a common LOLBin technique",
  "risk_score": 73,
  "severity": "high",
  "type": "eql",
  "query": "process where event.type == \"start\" and process.name == \"certutil.exe\" and process.args : (\"-urlcache\", \"-split\", \"-decode\") and not process.parent.name : (\"ccmexec.exe\", \"sccm*.exe\")",
  "threat": [
    {
      "framework": "MITRE ATT&CK",
      "tactic": {
        "id": "TA0011",
        "name": "Command and Control"
      },
      "technique": [
        {
          "id": "T1105",
          "name": "Ingress Tool Transfer"
        }
      ]
    }
  ],
  "tags": ["Hunting", "LOLBins", "T1105"],
  "interval": "5m",
  "from": "now-6m",
  "enabled": true
}

Deploy via Elastic Security API:

bash
curl -X POST "https://kibana:5601/api/detection_engine/rules" \
  -H "kbn-xsrf: true" \
  -H "Content-Type: application/json" \
  -H "Authorization: ApiKey YOUR_API_KEY" \
  -d @certutil_rule.json

Step 6: Aggregate and Visualize Findings

Create hunting dashboard with aggregations:

json
GET logs-endpoint.events.process-*/_search
{
  "size": 0,
  "query": {
    "bool": {
      "must": [
        {"term": {"process.name": "certutil.exe"}},
        {"range": {"@timestamp": {"gte": "now-30d"}}}
      ]
    }
  },
  "aggs": {
    "by_host": {
      "terms": {"field": "host.name", "size": 20},
      "aggs": {
        "by_user": {
          "terms": {"field": "user.name", "size": 10}
        },
        "by_args": {
          "terms": {"field": "process.args", "size": 10}
        }
      }
    }
  }
}

Step 7: Document Hunt and Close Loop

Record findings in a structured hunt report and update detection coverage:

• Hypothesis validated or refuted
• IOCs and affected hosts discovered
• Detection rules created or updated
• ATT&CK Navigator layer updated with new coverage
• Recommendations for security control improvements

Key Concepts

| Term | Definition | |------|-----------| | KQL | Kibana Query Language — simplified query syntax for filtering data in Kibana Discover and dashboards | | EQL | Event Query Language — Elastic's sequence-aware query language for detecting multi-step attack patterns | | ECS | Elastic Common Schema — standardized field naming convention enabling cross-source correlation | | Timeline | Elastic Security investigation workspace for collaborative event analysis and annotation | | Hypothesis-Driven Hunting | Structured approach starting with a theory about attacker behavior, tested against telemetry data | | LOLBins | Living Off the Land Binaries — legitimate Windows tools (certutil, mshta, rundll32) abused by attackers |

Tools & Systems

• Elastic Security: SIEM platform built on Elasticsearch with detection rules, Timeline, and case management
• Elastic Agent: Unified data collection agent replacing Beats for endpoint and network telemetry
• Elastic Endpoint Security: EDR capabilities integrated into Elastic Agent for process, file, and network monitoring
• ATT&CK Navigator: MITRE tool for tracking detection and hunting coverage across the ATT&CK matrix

Common Scenarios

• LOLBin Abuse: Hunt for mshta.exe, regsvr32.exe, rundll32.exe, certutil.exe with suspicious arguments
• Persistence Mechanisms: Query for scheduled task creation, registry run key modification, WMI subscriptions
• C2 Beaconing: Analyze network flow data for periodic outbound connections with consistent intervals
• Data Staging: Hunt for large file compression (7z, rar, zip) followed by outbound transfers
• Account Manipulation: Search for net.exe user creation, group membership changes, or password resets by non-admin users

Output Format

THREAT HUNT REPORT — TH-2024-012
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Hypothesis:   Attackers using certutil.exe for tool download (T1105)
Period:       2024-02-15 to 2024-03-15
Data Sources: Elastic Endpoint (process events), Sysmon

Findings:
  Total certutil executions:     342
  With -urlcache flag:           12 (3.5%)
  Suspicious (non-SCCM):        3 confirmed anomalous

Affected Hosts:
  WORKSTATION-042 (Finance)  — certutil downloading payload.exe from external IP
  SERVER-DB-03 (Database)    — certutil decoding base64 encoded binary
  LAPTOP-EXEC-07 (Executive) — certutil downloading script from Pastebin

Actions Taken:
  [DONE] 3 hosts isolated for forensic investigation
  [DONE] Detection rule "Certutil Download Activity" deployed (ID: elastic-th012)
  [DONE] ATT&CK Navigator updated: T1105 coverage = GREEN

Verdict:      HYPOTHESIS CONFIRMED — 3 true positive findings escalated to IR