Skills
skills/vercel-labs/vercel-plugin/vercel-firewall

vercel-firewall

SKILL.md

Vercel Firewall

You are an expert in the Vercel Firewall — a multi-layered security solution with automatic DDoS protection, a customizable Web Application Firewall (WAF), bot management, and rate limiting.

Architecture & Rule Execution Order

  1. DDoS mitigation rules (automatic, platform-wide)
  2. WAF IP blocking rules
  3. WAF custom rules (in priority order)
  4. WAF Managed Rulesets (OWASP, Bot Protection, AI Bots)

Changes propagate globally in under 300ms. No redeployment required.

DDoS Protection (Automatic, All Plans)

  • Layer 3/4 mitigation (automatic, always on)
  • Layer 7 protection (proprietary, tailored to web apps)
  • Protectd: Vercel's DoS mitigation infrastructure analyzes ~550K events/sec globally with median mitigation time of 2.5 seconds
  • 40x faster detection with real-time stream processing
  • Handles 1B+ suspicious TCP connections per week
  • Proven to mitigate 1.37 Tbps attacks with zero downtime

No configuration needed — DDoS protection is always active.

WAF Custom Rules

Rule JSON Structure

{
  "name": "Block WordPress scanners",
  "description": "Block common WordPress probe paths",
  "active": true,
  "conditionGroup": [
    {
      "conditions": [
        {
          "type": "path",
          "op": "re",
          "value": "^/wp-(admin|login|content|includes)/"
        }
      ]
    }
  ],
  "action": {
    "mitigate": {
      "action": "deny"
    }
  }
}

Logic: Each object in conditionGroup is an OR group. Conditions within a single group are ANDed. Multiple groups are ORed.

Condition Types (25 available)

Type Description Extra Fields
path URL path
method HTTP method
host Hostname
ip_address Client IP (supports CIDR)
user_agent User-Agent string
header Request header value key (header name)
query Query string parameter key (param name)
cookie Cookie value key (cookie name)
geo_country ISO country code (e.g., US)
geo_continent Continent code (e.g., NA)
geo_country_region State/province code
geo_city City name
geo_as_number ASN
ja4_digest JA4 TLS fingerprint
ja3_digest JA3 TLS fingerprint
target_path Resolved path after routing
route Matched route pattern
raw_path Raw unparsed path
region Vercel edge region code
protocol http/https
scheme URL scheme
environment Deployment environment
bot_name Specific bot name
bot_category Bot category
server_action Next.js Server Action ID

Condition Operators

Op Meaning
eq Equals
neq Not equals
re Regex match
pre Starts with
suf Ends with
sub Contains
inc In array
ninc Not in array
ex Exists
nex Not exists
gt / gte Greater than (or equal)
lt / lte Less than (or equal)

Additional optional fields: neg: true negates the condition, key required for header/query/cookie types.

Mitigation Actions

Action Description
log Log only, allow traffic
deny Block request (403)
challenge JavaScript browser challenge
bypass Skip all subsequent WAF rules
rate_limit Apply rate limiting (requires rateLimit config)
redirect Redirect (requires redirect config)

Persistent Actions

By default each request is evaluated individually. With persistent actions, rules are applied to all matching requests for a customizable duration (actionDuration), allowing the firewall to remember malicious behavior and block it earlier in the lifecycle.

Action Options

{
  "action": {
    "mitigate": {
      "action": "deny",
      "actionDuration": "1h",
      "bypassSystem": false,
      "logHeaders": ["user-agent", "x-forwarded-for"],
      "redirect": {
        "location": "https://example.com/blocked",
        "permanent": false
      }
    }
  }
}

Practical Rule Examples

Block Sanctioned Countries

{
  "name": "Block OFAC Sanctioned Countries",
  "active": true,
  "conditionGroup": [
    {
      "conditions": [
        {
          "type": "geo_country",
          "op": "inc",
          "value": ["CU", "IR", "KP", "RU", "SY"]
        }
      ]
    }
  ],
  "action": {
    "mitigate": { "action": "deny" }
  }
}

Require API Key Header on /api/ Routes

{
  "name": "Require API Key",
  "active": true,
  "conditionGroup": [
    {
      "conditions": [
        {
          "type": "header",
          "op": "nex",
          "key": "x-api-key"
        },
        {
          "type": "path",
          "op": "pre",
          "value": "/api/"
        }
      ]
    }
  ],
  "action": {
    "mitigate": { "action": "deny" }
  }
}

Block by JA4 TLS Fingerprint

{
  "name": "Block Known Malicious JA4",
  "active": true,
  "conditionGroup": [
    {
      "conditions": [
        {
          "type": "ja4_digest",
          "op": "eq",
          "value": "t13d1516h2_8daaf6152771_b0da82dd1658"
        }
      ]
    }
  ],
  "action": {
    "mitigate": { "action": "deny", "actionDuration": "1h" }
  }
}

Block Datacenter ASNs

{
  "name": "Block Known Datacenter ASNs",
  "active": true,
  "conditionGroup": [
    {
      "conditions": [
        {
          "type": "geo_as_number",
          "op": "inc",
          "value": ["14618", "16509", "15169"]
        }
      ]
    }
  ],
  "action": {
    "mitigate": { "action": "deny" }
  }
}

Challenge cURL Requests

{
  "name": "Challenge cURL",
  "active": true,
  "conditionGroup": [
    {
      "conditions": [
        { "type": "user_agent", "op": "re", "value": "^curl/" }
      ]
    }
  ],
  "action": {
    "mitigate": { "action": "challenge" }
  }
}

Rate Limiting

Rate Limit Rule

{
  "name": "API Rate Limit - 100 req/min",
  "active": true,
  "conditionGroup": [
    {
      "conditions": [
        { "type": "path", "op": "pre", "value": "/api/" }
      ]
    }
  ],
  "action": {
    "mitigate": {
      "action": "rate_limit",
      "rateLimit": {
        "algo": "fixed_window",
        "window": 60,
        "limit": 100,
        "keys": ["ip"],
        "action": "deny"
      }
    }
  }
}

Login Endpoint Protection

{
  "name": "Login Rate Limit",
  "active": true,
  "conditionGroup": [
    {
      "conditions": [
        { "type": "path", "op": "eq", "value": "/api/auth/login" },
        { "type": "method", "op": "eq", "value": "POST" }
      ]
    }
  ],
  "action": {
    "mitigate": {
      "action": "rate_limit",
      "rateLimit": {
        "algo": "fixed_window",
        "window": 60,
        "limit": 10,
        "keys": ["ip"],
        "action": "challenge"
      }
    }
  }
}

Rate Limit Configuration Options

Field Type Description
algo string "fixed_window" (all plans) or "token_bucket" (Enterprise)
window number Seconds. Min 10, max 600 (Pro), max 3600 (Enterprise)
limit number Max requests per window
keys array Count per: "ip", "ja4", "user_agent", custom headers (Enterprise)
action string When exceeded: "deny", "log", "challenge"

When exceeded with deny, returns HTTP 429 with X-RateLimit-Limit and X-RateLimit-Remaining headers.

Bot Management

Bot Protection (GA — Free on All Plans)

Heuristics-based detection that challenges non-browser bot traffic without disrupting verified webhook providers. Formerly "Bot Filter" during beta — renamed to Bot Protection at GA. Enable in log-only mode first to preview traffic impact:

{
  "action": "managedRules.update",
  "id": "bot_protection",
  "value": { "active": true, "action": "challenge" }
}

Note: The older bot_filter ID is deprecated. Use bot_protection in new configurations.

AI Bot Blocking

Block known AI crawlers (GPTBot, ClaudeBot, etc.):

{
  "action": "managedRules.update",
  "id": "ai_bots",
  "value": { "active": true, "action": "deny" }
}

Allow a Specific Bot (Bypass Rule)

Place this higher in priority than Bot Protection managed rules:

{
  "name": "Allow My Monitoring Bot",
  "active": true,
  "conditionGroup": [
    {
      "conditions": [
        { "type": "user_agent", "op": "eq", "value": "MyMonitorBot/1.0" }
      ]
    }
  ],
  "action": {
    "mitigate": { "action": "bypass" }
  }
}

Enable BotID (Traffic Visibility)

{ "botIdEnabled": true }

IP Allow/Block Lists

Block an IP

{
  "action": "ip.insert",
  "value": {
    "hostname": "my-site.com",
    "ip": "203.0.113.45",
    "action": "deny",
    "notes": "Malicious scraper"
  }
}

Block a CIDR Range

{
  "action": "ip.insert",
  "value": {
    "hostname": "my-site.com",
    "ip": "203.0.113.0/24",
    "action": "deny",
    "notes": "Bad actor CIDR block"
  }
}

Allow an IP (Bypass All Rules)

{
  "action": "ip.insert",
  "value": {
    "hostname": "my-site.com",
    "ip": "198.51.100.1",
    "action": "bypass",
    "notes": "Internal monitoring IP"
  }
}

IP Rule Actions

Action Effect
deny Block the IP
challenge Serve JS challenge
log Log traffic only
bypass Allow through all rules (allowlist)

Note: hostname must match the exact domain. Add separate entries per subdomain.

OWASP Core Ruleset (CRS)

Individual CRS Rules

ID Protection
sqli SQL Injection
xss Cross-Site Scripting
rce Remote Code Execution
lfi Local File Inclusion
rfi Remote File Inclusion
sd Scanner Detection
ma Multipart Attack
php PHP-specific exploits
gen Generic attack patterns
sf Session Fixation
java Java-specific exploits

Enable OWASP Rules

{
  "action": "crs.update",
  "id": "sqli",
  "value": { "active": true, "action": "deny" }
}

Full OWASP + Bot Configuration (PUT)

{
  "firewallEnabled": true,
  "crs": {
    "sqli": { "active": true, "action": "deny" },
    "xss": { "active": true, "action": "deny" },
    "rce": { "active": true, "action": "deny" },
    "lfi": { "active": true, "action": "deny" },
    "rfi": { "active": true, "action": "deny" },
    "sd": { "active": true, "action": "log" },
    "ma": { "active": true, "action": "deny" },
    "gen": { "active": true, "action": "deny" },
    "sf": { "active": true, "action": "deny" },
    "php": { "active": false, "action": "log" },
    "java": { "active": false, "action": "log" }
  },
  "managedRules": {
    "owasp": { "active": true, "action": "deny" },
    "bot_protection": { "active": true, "action": "challenge" },
    "ai_bots": { "active": true, "action": "deny" }
  },
  "botIdEnabled": true
}

Firewall REST API

Base URL: https://api.vercel.com Auth: Authorization: Bearer <VERCEL_TOKEN> Query params: ?projectId=<id>&teamId=<id>

Endpoints

Method Path Description
GET /v1/security/firewall/config/active Read current config
PATCH /v1/security/firewall/config Incremental update (add/remove/update rules)
PUT /v1/security/firewall/config Full config replacement
POST /v1/security/firewall/bypass Create temporary bypass rule

PATCH Actions

Action Description
firewallEnabled Enable/disable firewall (value: boolean)
rules.insert Add a custom rule
rules.update Update rule (requires id)
rules.remove Delete rule (requires id)
rules.priority Reorder rule (requires id, value = index)
ip.insert Add IP rule
ip.update Update IP rule
ip.remove Delete IP rule
crs.update Enable/configure OWASP CRS rule
crs.disable Disable entire CRS
managedRules.update Configure managed ruleset

Add a Rule via cURL

curl -X PATCH "https://api.vercel.com/v1/security/firewall/config?projectId=prj_xxx&teamId=team_xxx" \
  -H "Authorization: Bearer $VERCEL_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "action": "rules.insert",
    "value": {
      "name": "Block WordPress scanners",
      "active": true,
      "conditionGroup": [
        {
          "conditions": [
            { "type": "path", "op": "re", "value": "^/wp-(admin|login|content|includes)/" }
          ]
        }
      ],
      "action": { "mitigate": { "action": "deny" } }
    }
  }'

Vercel SDK Usage

import { Vercel } from '@vercel/sdk'

const vercel = new Vercel({ bearerToken: process.env.VERCEL_TOKEN })

// Read current firewall config
const config = await vercel.security.readFirewallConfig({
  configVersion: 'active',
  projectId: 'prj_xxx',
  teamId: 'team_xxx',
})

// Add a rule
await vercel.security.updateFirewallConfig({
  projectId: 'prj_xxx',
  teamId: 'team_xxx',
  requestBody: {
    action: 'rules.insert',
    value: {
      name: 'Rate limit API',
      active: true,
      conditionGroup: [
        { conditions: [{ type: 'path', op: 'pre', value: '/api/' }] },
      ],
      action: {
        mitigate: {
          action: 'rate_limit',
          rateLimit: { algo: 'fixed_window', window: 60, limit: 100, keys: ['ip'], action: 'deny' },
        },
      },
    },
  },
})

Create Temporary Bypass (Attack Challenge Mode)

curl -X POST "https://api.vercel.com/v1/security/firewall/bypass?projectId=prj_xxx&teamId=team_xxx" \
  -H "Authorization: Bearer $VERCEL_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "domain": "my-site.com",
    "sourceIp": "198.51.100.42",
    "ttl": 3600000,
    "note": "Temporary bypass for load testing"
  }'

vercel.json WAF Rules

Declaratively define firewall rules in vercel.json using the mitigate key:

{
  "$schema": "https://openapi.vercel.sh/vercel.json",
  "routes": [
    {
      "src": "/api/(.*)",
      "missing": [
        { "type": "header", "key": "x-internal-token" }
      ],
      "mitigate": { "action": "deny" }
    },
    {
      "src": "/(.*)",
      "has": [
        { "type": "header", "key": "user-agent", "value": "(?i)^curl/" }
      ],
      "mitigate": { "action": "challenge" }
    }
  ]
}

Supported actions in vercel.json: "challenge", "deny" only. Rate limiting, log, and bypass require the Vercel Firewall dashboard at https://vercel.com/{team}/{project}/firewall or the REST API.

Attack Challenge Mode

  • Available on all plans (free)
  • Shows browser verification challenge to all visitors during active attacks
  • Legitimate bots (Googlebot, webhook providers) automatically pass through
  • Internal Function-to-Function calls within the same account bypass automatically
  • Blocked requests don't count toward CDN/traffic usage
  • Configured via dashboard only: open https://vercel.com/{team}/{project}/firewall → Bot Management → Attack Challenge Mode

Plan Availability

Feature Hobby Pro Enterprise
DDoS Protection All All All
Custom Rules 5 40 1000
Rate Limiting 1 rule 40 rules 1000 rules
Bot Protection (GA) Yes Yes Yes
OWASP CRS — — Yes
Token Bucket algo — — Yes
Custom rate limit keys — — Yes

Observability

  • Security event logs in the Firewall tab
  • IP enrichment — hover any IP in the Firewall dashboard to see ASN, location, and metadata
  • Create custom WAF rules directly from dashboard traffic charts (select "Create Custom Rule" from the actions menu)
  • Linkable to Monitoring queries for investigations
  • DDoS mitigation notifications (alerts on detection)
  • BotID traffic visibility when enabled

Official Documentation

Weekly Installs
7
Repository
vercel-labs/ver…l-plugin
GitHub Stars
7
First Seen
9 days ago
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