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

• Vercel Firewall Overview
• Custom Rules
• Rate Limiting
• IP Blocking
• Managed Rulesets
• Attack Challenge Mode
• Firewall API Guide
• REST API Reference