Incident response automation

interface SecurityEvent {
  id: string;
  timestamp: string;
  source: string; // e.g., 'edr', 'cloudtrail', 'siem'
  eventType: string;
  severity: 'low' | 'medium' | 'high' | 'critical';
  entity: {
    type: 'host' | 'user' | 'ip' | 'domain';
    value: string;
    metadata: Record<string, unknown>;
  };
  context: Record<string, unknown>;
}

export const normalizeEvent = (raw: unknown): SecurityEvent => {
  if (!raw || typeof raw !== 'object') throw new Error('Invalid event payload');
  const payload = raw as Record<string, unknown>;
  
  return {
    id: crypto.randomUUID(),
    timestamp: new Date().toISOString(),
    source: String(payload.source || 'unknown'),
    eventType: String(payload.event_type || 'unknown'),
    severity: (['low', 'medium', 'high', 'critical'].includes(String(payload.severity)) 
      ? String(payload.severity) as SecurityEvent['severity'] 
      : 'low'),
    entity: {
      type: String(payload.entity_type || 'host') as SecurityEvent['entity']['type'],
      value: String(payload.entity_value || ''),
      metadata: (payload.metadata || {}) as Record<string, unknown>,
    },
    context: (payload.context || {}) as Record<string, unknown>,
  };
};

import { Redis } from 'ioredis';

const redis = new Redis(process.env.REDIS_URL);

export class EnrichmentService {
  async enrich(event: SecurityEvent): Promise<SecurityEvent & { riskScore: number; approved: boolean }> {
    const [threatIntel, assetProfile, history] = await Promise.all([
      this.queryThreatIntel(event.entity.value),
      this.queryAssetInventory(event.entity.value),
      this.queryHistoricalBehavior(event.entity.value),
    ]);

    const riskScore = this.calculateRiskScore(event, threatIntel, assetProfile, history);
    const approved = riskScore >= 75 && !assetProfile.isProductionCritical;

    await redis.setex(`event:${event.id}`, 3600, JSON.stringify({ ...event, riskScore, approved }));

    return { ...event, riskScore, appro

ved }; }

private calculateRiskScore( event: SecurityEvent, threatIntel: { isMalicious: boolean; confidence: number }, asset: { criticality: number; lastPatch: string }, history: { previousIncidents: number; avgResponseTime: number } ): number { let score = 0; if (event.severity === 'critical') score += 30; if (event.severity === 'high') score += 20; if (threatIntel.isMalicious) score += threatIntel.confidence * 0.5; if (asset.criticality > 8) score -= 15; // Lower auto-approval for critical assets if (history.previousIncidents > 3) score += 10; return Math.min(100, Math.max(0, score)); } }

### Step 3: Playbook Orchestration
Playbooks must be stateful, idempotent, and support conditional branching. Use a deterministic runner that validates execution prerequisites, applies blast-radius controls, and logs every action.

```typescript
export interface PlaybookAction {
  id: string;
  type: 'isolate_host' | 'revoke_token' | 'block_ip' | 'create_ticket';
  target: string;
  parameters: Record<string, unknown>;
  rollback?: PlaybookAction;
}

export class PlaybookRunner {
  private readonly executionLog: Map<string, Set<string>> = new Map();

  async execute(eventId: string, actions: PlaybookAction[]): Promise<void> {
    const executed = this.executionLog.get(eventId) ?? new Set();
    
    for (const action of actions) {
      if (executed.has(action.id)) continue; // Idempotency guard

      try {
        await this.executeAction(action);
        executed.add(action.id);
        this.executionLog.set(eventId, executed);
        console.info(`Executed action ${action.id} for event ${eventId}`);
      } catch (err) {
        console.error(`Action ${action.id} failed: ${(err as Error).message}`);
        if (action.rollback) {
          await this.executeAction(action.rollback);
          console.warn(`Executed rollback for action ${action.id}`);
        }
        throw err;
      }
    }
  }

  private async executeAction(action: PlaybookAction): Promise<void> {
    switch (action.type) {
      case 'isolate_host':
        // EDR API call with timeout & retry
        break;
      case 'revoke_token':
        // IAM/Identity provider call
        break;
      case 'block_ip':
        // WAF/Firewall API call
        break;
      case 'create_ticket':
        // Jira/ServiceNow integration
        break;
      default:
        throw new Error(`Unsupported action type: ${action.type}`);
    }
  }
}

Architecture Decisions & Rationale

• Event-Driven Decoupling: Ingestion, enrichment, and execution run as independent services communicating via message queues or event buses. This prevents cascading failures and allows independent scaling during alert storms.
• Idempotency Enforcement: Security actions must be safe to retry. The runner tracks executed action IDs per event, preventing duplicate isolations, revocations, or firewall blocks that could cause operational disruption.
• Deterministic Scoring over ML-Only Triage: Machine learning models introduce opacity and drift. A hybrid approach uses deterministic risk scoring for automation gates, reserving ML for anomaly detection and post-incident analysis. This ensures predictable blast radius and compliance auditability.
• Stateless Execution with External State: The runner remains stateless; execution history, risk scores, and playbook states are persisted in Redis or a durable store. This enables horizontal scaling, crash recovery, and audit trail generation without coupling execution logic to storage.

Pitfall Guide

1. Automating Without Blast-Radius Controls Executing containment actions on production-critical assets without validation causes outages. Always implement asset criticality checks and environment-aware routing before triggering remediation.

2. Ignoring Alert Storms & Correlation Running playbooks per raw alert floods APIs and exhausts rate limits. Implement event correlation windows (e.g., 5-minute deduplication) and circuit breakers that pause automation when event velocity exceeds thresholds.

3. State Drift & Missing Idempotency Retrying failed actions without tracking execution state results in duplicate blocks, revoked tokens, or isolated hosts. Enforce idempotency keys and maintain an execution ledger.

4. Over-Reliance on Single Enrichment Source Depending on one threat intelligence feed or asset inventory creates blind spots. Aggregate multiple sources with fallback scoring and cache enrichment results to reduce latency.

5. Bypassing Audit Trails Security automation must be fully auditable. Every decision, score calculation, action execution, and rollback must be logged with timestamps, actor/service identity, and input parameters.

6. No Rollback or Compensating Actions Automation failures leave systems in inconsistent states. Define explicit rollback actions for every containment step and test them during tabletop exercises.

7. Misplaced Human-in-the-Loop Gates Requiring manual approval for low-severity events creates bottlenecks; skipping approval for critical assets introduces risk. Route based on severity, asset criticality, and historical confidence scores.

Best Practices from Production:

• Version control all playbook definitions and enforce peer review before deployment.
• Implement dry-run mode for new playbooks; log actions without executing them for 7-14 days.
• Use structured logging with correlation IDs to trace events from ingestion to remediation.
• Run monthly automation health checks: verify API credentials, validate enrichment cache freshness, and test rollback paths.

Production Bundle

Action Checklist

• Define automation scope: restrict to non-production assets and low/medium severity initially
• Implement idempotency tracking: map action IDs to event IDs with TTL-based cleanup
• Set blast-radius limits: integrate asset criticality scoring and environment routing
• Deploy enrichment pipeline: aggregate threat intel, asset inventory, and historical behavior
• Enable comprehensive audit logging: capture decisions, scores, executions, and rollbacks
• Configure circuit breakers: pause automation during alert storms exceeding defined thresholds
• Run tabletop drills: simulate incidents weekly to validate playbook execution and rollback paths

Decision Matrix

Scenario	Recommended Approach	Why	Cost Impact
Low-severity, high-volume alerts	Fully automated triage & containment	Reduces engineer burnout; predictable blast radius	↓ 65% operational cost
Critical production assets	Human-in-the-loop with auto-enrichment	Prevents service disruption while accelerating decision context	↑ 15% tooling cost, ↓ 40% breach cost
Compliance-driven environments	Deterministic playbooks with dry-run validation	Ensures auditability and regulatory alignment	Neutral to ↓ 10% audit overhead
Resource-constrained teams	Rule-based automation + managed enrichment SaaS	Minimizes maintenance while delivering immediate MTTR reduction	↑ 20% SaaS cost, ↓ 50% headcount pressure

Configuration Template

playbook:
  id: IR-AUTO-042
  name: "Credential Compromise Containment"
  version: "1.3.0"
  triggers:
    - source: "edr"
      event_type: "credential_theft"
      severity: ["high", "critical"]
  conditions:
    asset_criticality: "<= 7"
    environment: ["staging", "dev", "sandbox"]
    risk_threshold: 75
  actions:
    - id: "revoke-session"
      type: "revoke_token"
      target: "{{ entity.value }}"
      parameters:
        provider: "identity_platform"
        scope: "active_sessions"
      rollback:
        id: "restore-session"
        type: "revoke_token"
        parameters:
          provider: "identity_platform"
          scope: "active_sessions"
          action: "restore"
    - id: "notify-channel"
      type: "create_ticket"
      target: "{{ entity.value }}"
      parameters:
        system: "jira"
        project: "SEC"
        priority: "{{ severity }}"
        labels: ["auto-remediated", "credential-theft"]
  gates:
    human_approval: false
    dry_run: false
    audit_log: true
  execution:
    idempotency: true
    timeout_seconds: 30
    retry_policy:
      max_attempts: 2
      backoff_ms: 1000

Quick Start Guide

1. Deploy the orchestration runner: Containerize the TypeScript playbook runner and deploy it to your Kubernetes cluster or serverless platform. Configure environment variables for Redis, EDR, and identity provider APIs.
2. Connect your ingestion webhook: Route SIEM/EDR alerts to the runner’s /ingest endpoint. Ensure payloads include source, event_type, severity, and entity fields matching the normalized schema.
3. Load the baseline playbook: Import the configuration template above via the runner’s /playbooks API. Enable dry-run mode initially to validate scoring and routing without executing actions.
4. Execute a controlled test: Trigger a simulated credential theft event using your EDR’s test console or a curl payload. Verify enrichment scoring, idempotency logging, and audit trail generation. Switch dry_run: false once validation passes.