Implementing SIEM Use Cases for Detection

When to Use

Use this skill when:

• SOC teams need to build or expand their SIEM detection library from scratch
• Threat assessments identify ATT&CK technique gaps requiring new detection rules
• Detection engineers need a structured process for use case design, testing, and deployment
• Compliance requirements mandate specific detection capabilities (PCI DSS, HIPAA, SOX)

Do not use for ad-hoc hunting queries — use cases are formalized, tested, and maintained detection rules, not exploratory searches.

Prerequisites

• SIEM platform (Splunk ES, Elastic Security, or Microsoft Sentinel) with production data
• ATT&CK Navigator for coverage gap analysis
• Log sources normalized to CIM/ECS field standards
• Use case documentation framework (wiki, Git repo, or detection engineering platform)
• Testing environment with attack simulation tools (Atomic Red Team, MITRE Caldera)

Workflow

Step 1: Assess Detection Coverage Gaps

Map current detection rules to ATT&CK and identify gaps:

import json

# Load current detection rules mapped to ATT&CK
current_rules = [
    {"name": "Brute Force Detection", "techniques": ["T1110.001", "T1110.003"]},
    {"name": "Malware Hash Match", "techniques": ["T1204.002"]},
    {"name": "Suspicious PowerShell", "techniques": ["T1059.001"]},
]

# Load ATT&CK Enterprise techniques
with open("enterprise-attack.json") as f:
    attack = json.load(f)

all_techniques = set()
for obj in attack["objects"]:
    if obj["type"] == "attack-pattern":
        ext = obj.get("external_references", [])
        for ref in ext:
            if ref.get("source_name") == "mitre-attack":
                all_techniques.add(ref["external_id"])

covered = set()
for rule in current_rules:
    covered.update(rule["techniques"])

gaps = all_techniques - covered
print(f"Total techniques: {len(all_techniques)}")
print(f"Covered: {len(covered)} ({len(covered)/len(all_techniques)*100:.1f}%)")
print(f"Gaps: {len(gaps)}")

# Prioritize gaps by threat relevance
priority_techniques = [
    "T1003", "T1021", "T1053", "T1547", "T1078",
    "T1055", "T1071", "T1105", "T1036", "T1070"
]
priority_gaps = [t for t in priority_techniques if t in gaps]
print(f"Priority gaps: {priority_gaps}")

Step 2: Design Use Case Specification

Document each use case with a standardized template:

use_case_id: UC-2024-015
name: Credential Dumping via LSASS Access
description: Detects tools accessing LSASS process memory for credential extraction
mitre_attack:
  tactic: Credential Access (TA0006)
  technique: T1003.001 - LSASS Memory
  data_sources:
    - Process: OS API Execution (Sysmon EventCode 10)
    - Process: Process Access (Windows Security 4663)
log_sources:
  - index: sysmon, sourcetype: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
  - index: wineventlog, sourcetype: WinEventLog:Security
severity: High
confidence: Medium-High
false_positive_sources:
  - Antivirus products scanning LSASS
  - CrowdStrike Falcon sensor
  - Windows Defender ATP
  - SCCM client
tuning_notes: >
  Maintain exclusion list for known security tools that legitimately access LSASS.
  Review exclusions quarterly for newly deployed security products.
sla: Alert within 5 minutes of detection
owner: detection_engineering_team
status: Production
created: 2024-03-15
last_tested: 2024-03-15

Step 3: Implement Detection Logic Across Platforms

Splunk ES Correlation Search:

| tstats summariesonly=true count from datamodel=Endpoint.Processes
  where Processes.process_name="lsass.exe"
  by Processes.dest, Processes.user, Processes.process_name,
     Processes.parent_process_name, Processes.parent_process
| `drop_dm_object_name(Processes)`
| lookup lsass_access_whitelist parent_process AS parent_process OUTPUT is_whitelisted
| where isnull(is_whitelisted) OR is_whitelisted!="true"
| `credential_dumping_lsass_filter`

Or using raw Sysmon data:

index=sysmon EventCode=10 TargetImage="*\\lsass.exe"
GrantedAccess IN ("0x1010", "0x1038", "0x1fffff", "0x40")
NOT [| inputlookup lsass_whitelist.csv | fields SourceImage]
| stats count, values(GrantedAccess) AS access_flags by Computer, SourceImage, SourceUser
| where count > 0

Elastic Security EQL Rule:

process where event.type == "access" and
  process.name == "lsass.exe" and
  not process.executable : (
    "?:\\Windows\\System32\\svchost.exe",
    "?:\\Windows\\System32\\csrss.exe",

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