DDoS Protection Patterns

DDoS Protection Patterns

Allowlist Trusted IPs

const config = {
  description: 'Allowlist trusted IPs',
  rules: [
    {
      expression: 'ip.src in { 203.0.113.0/24 192.0.2.1 }',
      action: 'execute',
      action_parameters: {
        id: managedRulesetId,
        overrides: { sensitivity_level: 'eoff' },
      },
    },
  ],
}

await client.accounts.rulesets.phases.entrypoint.update('ddos_l7', {
  account_id: accountId,
  ...config,
})

Route-specific Sensitivity

const config = {
  description: 'Route-specific protection',
  rules: [
    {
      expression: 'not http.request.uri.path matches "^/api/"',
      action: 'execute',
      action_parameters: {
        id: managedRulesetId,
        overrides: { sensitivity_level: 'default', action: 'block' },
      },
    },
    {
      expression: 'http.request.uri.path matches "^/api/"',
      action: 'execute',
      action_parameters: {
        id: managedRulesetId,
        overrides: { sensitivity_level: 'low', action: 'managed_challenge' },
      },
    },
  ],
}

Progressive Enhancement

enum ProtectionLevel {
  MONITORING = 'monitoring',
  LOW = 'low',
  MEDIUM = 'medium',
  HIGH = 'high',
}

const levelConfig = {
  [ProtectionLevel.MONITORING]: { action: 'log', sensitivity: 'eoff' },
  [ProtectionLevel.LOW]: { action: 'managed_challenge', sensitivity: 'low' },
  [ProtectionLevel.MEDIUM]: { action: 'managed_challenge', sensitivity: 'medium' },
  [ProtectionLevel.HIGH]: { action: 'block', sensitivity: 'default' },
} as const

async function setProtectionLevel(zoneId: string, level: ProtectionLevel, rulesetId: string, client: Cloudflare) {
  const settings = levelConfig[level]
  return client.zones.rulesets.phases.entrypoint.update('ddos_l7', {
    zone_id: zoneId,
    rules: [
      {
        expression: 'true',
        action: 'execute',
        action_parameters: {
          id: rulesetId,
          overrides: { action: settings.action, sensitivity_level: settings.sensitivity },
        },
      },
    ],
  })
}

Dynamic Response to Attacks

interface Env {
  CLOUDFLARE_API_TOKEN: string
  ZONE_ID: string
  KV: KVNamespace
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    if (request.url.includes('/attack-detected')) {
      const attackData = await request.json()
      await env.KV.put(`attack:${Date.now()}`, JSON.stringify(attackData), { expirationTtl: 86400 })
      const recentAttacks = await getRecentAttacks(env.KV)
      if (recentAttacks.length > 5) {
        await setProtectionLevel(env.ZONE_ID, ProtectionLevel.HIGH, managedRulesetId, client)
        return new Response('Protection increased')
      }
    }
    return new Response('OK')
  },
  async scheduled(event: ScheduledEvent, env: Env): Promise<void> {
    const recentAttacks = await getRecentAttacks(env.KV)
    if (recentAttacks.length === 0)
      await setProtectionLevel(env.ZONE_ID, ProtectionLevel.MEDIUM, managedRulesetId, client)
  },
}

Multi-rule Tiered Protection (Enterprise Advanced)

const config = {
  description: 'Multi-tier DDoS protection',
  rules: [
    {
      expression: 'not ip.src in $known_ips and not cf.bot_management.score gt 30',
      action: 'execute',
      action_parameters: { id: managedRulesetId, overrides: { sensitivity_level: 'default', action: 'block' } },
    },
    {
      expression: 'cf.bot_management.verified_bot',
      action: 'execute',
      action_parameters: {
        id: managedRulesetId,
        overrides: { sensitivity_level: 'medium', action: 'managed_challenge' },
      },
    },
    {
      expression: 'ip.src in $trusted_ips',
      action: 'execute',
      action_parameters: { id: managedRulesetId, overrides: { sensitivity_level: 'low' } },
    },
  ],
}

Defense in Depth

Layered security stack: DDoS + WAF + Rate Limiting + Bot Management.

// Layer 1: DDoS (volumetric attacks)
await client.zones.rulesets.phases.entrypoint.update('ddos_l7', {
  zone_id: zoneId,
  rules: [
    {
      expression: 'true',
      action: 'execute',
      action_parameters: { id: ddosRulesetId, overrides: { sensitivity_level: 'medium' } },
    },
  ],
})

// Layer 2: WAF (exploit protection)
await client.zones.rulesets.phases.entrypoint.update('http_request_firewall_managed', {
  zone_id: zoneId,
  rules: [{ expression: 'true', action: 'execute', action_parameters: { id: wafRulesetId } }],
})

// Layer 3: Rate Limiting (abuse prevention)
await client.zones.rulesets.phases.entrypoint.update('http_ratelimit', {
  zone_id: zoneId,
  rules: [
    {
      expression: 'http.request.uri.path eq "/api/login"',
      action: 'block',
      ratelimit: { characteristics: ['ip.src'], period: 60, requests_per_period: 5 },
    },
  ],
})

// Layer 4: Bot Management (automation detection)
await client.zones.rulesets.phases.entrypoint.update('http_request_sbfm', {
  zone_id: zoneId,
  rules: [{ expression: 'cf.bot_management.score lt 30', action: 'managed_challenge' }],
})

Cache Strategy for DDoS Mitigation

Exclude query strings from cache key to counter randomized query parameter attacks.

const cacheRule = {
  expression: 'http.request.uri.path matches "^/api/"',
  action: 'set_cache_settings',
  action_parameters: {
    cache: true,
    cache_key: { ignore_query_strings_order: true, custom_key: { query_string: { exclude: { all: true } } } },
  },
}

await client.zones.rulesets.phases.entrypoint.update('http_request_cache_settings', {
  zone_id: zoneId,
  rules: [cacheRule],
})

Rationale: Attackers randomize query strings (?random=123456) to bypass cache. Excluding query params ensures cache hits absorb attack traffic.

See configuration.md for rule structure details.