The Datacenter Traffic Vector

Legitimate human users rarely browse the internet through datacenter IP ranges (e.g., AWS, DigitalOcean, Hetzner). Conversely, over 90% of credential stuffing attacks, aggressive scrapers, and DDoS botnets originate from these ASNs due to the low cost of cloud compute.

Blocking datacenter IPs is one of the highest-ROI security signals available. However, a blanket ban on all datacenter ASNs introduces a critical risk: blocking legitimate non-human traffic, such as payment webhooks (Stripe, PayPal), CI/CD pipelines, and search engine crawlers.

To implement this successfully, you must move from Blocking ASNs to Contextual IP Intelligence.

Strategy: Detection and Exception

The architecture for precision blocking requires three steps:

Identification: Query an IP intelligence provider to determine if the ingress IP belongs to a hosting provider.
Allowlisting: Check the IP against a list of known "good bots" (Googlebot, Bingbot) and critical infrastructure partners.
Enforcement: Drop the connection or challenge the user (CAPTCHA) if the IP is a datacenter but not on the allowlist.

Implementation: Node.js Middleware

The following Express.js middleware demonstrates how to integrate IPASIS to filter requests. It assumes the use of a local LRU cache to minimize API latency.

const axios = require('axios');
const LRU = require('lru-cache');

// Initialize cache: 500 items, 1 hour TTL
const ipCache = new LRU({ max: 500, ttl: 1000 * 60 * 60 });

// Trusted User Agents (Regex for performance)
const TRUSTED_BOTS = /Googlebot|Bingbot|DuckDuckBot/;

async function datacenterFirewall(req, res, next) {
    const ip = req.ip;

    // 1. Check Allowlist (User-Agent verification recommended alongside IP check)
    const userAgent = req.get('User-Agent');
    if (TRUSTED_BOTS.test(userAgent)) {
        // Note: For strict security, verify the IP actually belongs to Google/Bing via reverse DNS
        return next();
    }

    // 2. Check Cache
    if (ipCache.has(ip)) {
        const cachedData = ipCache.get(ip);
        if (cachedData.block) return res.status(403).json({ error: 'Access Denied' });
        return next();
    }

    // 3. Query IPASIS API
    try {
        const response = await axios.get(`https://api.ipasis.com/v1/${ip}`, {
            headers: { 'X-API-Key': process.env.IPASIS_KEY }
        });

        const { is_datacenter, is_crawler } = response.data;

        // Logic: Block if datacenter, UNLESS it is a verified crawler
        const shouldBlock = is_datacenter && !is_crawler;

        ipCache.set(ip, { block: shouldBlock });

        if (shouldBlock) {
            return res.status(403).json({ error: 'VPN/Datacenter traffic not permitted.' });
        }

        next();
    } catch (error) {
        // Fail open to prevent downtime during API outages
        console.error('IP Intelligence lookup failed:', error.message);
        next();
    }
}

module.exports = datacenterFirewall;

Handling Edge Cases

Corporate VPNs and SASE

Some enterprise users route traffic through cloud-based SASE providers (e.g., Zscaler, Palo Alto Networks Prisma). These often appear as datacenter IPs.

Mitigation: IPASIS differentiates between Hosting and Business types. Refine the blocking logic to allow usage_type: "corporate" while blocking usage_type: "hosting".

Webhooks and APIs

If your application consumes webhooks (e.g., Stripe events), these requests will originate from datacenter IPs.

Mitigation: Do not apply the firewall to specific API routes (e.g., /api/webhooks/*). Alternatively, validate the X-Signature headers provided by the vendor before IP checking.

FAQ

Q: Why not just block AWS and Azure ASNs using a static list?

Static lists become outdated within days. Cloud providers constantly acquire new prefixes and recycle old ones. An API-based approach ensures you are filtering based on real-time BGP data.

Q: Will this block legitimate SEO crawlers?

It can if you rely solely on is_datacenter. You must use the is_crawler attribute provided by IPASIS, or manually verify that the IP belongs to a known search engine via reverse DNS (rDNS) lookups.

Q: Does this introduce latency?

Fetching external data adds network overhead. However, by implementing an LRU cache (as shown in the code snippet) or using a Redis layer, you only incur that latency once per IP session. The impact on P99 latency is negligible for repeat traffic.

Secure Your Perimeter with Data, Not Guesswork

Stop chasing IP lists and start making decisions based on accurate infrastructure intelligence.

Get your free API Key from IPASIS and start filtering high-risk datacenter traffic today.

Mitigating Automated Threats: Precision Blocking of Datacenter IPs