What is a Proxy?

A proxy is an intermediary server or service that forwards requests from clients to other servers. It can be used to mask the client's identity, filter traffic, cache content, or enforce security policies. Proxies are widely used in networking, web development, and security architectures.

Types of proxy

Proxies fall into a handful of distinct categories depending on where they sit in the request flow and what they're trying to achieve.

• Forward proxy — sits between a client and the wider internet, typically used inside corporate networks to filter outbound traffic, cache common resources, or enforce policy.
• Reverse proxy — sits in front of one or more origin servers, terminating client connections and routing them to backend services. Reverse proxies are how products like Nginx, HAProxy and Cloudflare deliver load balancing, TLS termination and caching at scale.
• Transparent proxy — intercepts traffic without requiring client configuration. Often deployed by ISPs and organisations for monitoring or content filtering.
• Anonymous and elite proxies — strip or mask identifying headers so the origin server can't tell that traffic was proxied. These are commonly sold as part of consumer "anonymising" services.
• Residential proxies — relay traffic through real consumer IP addresses (often via opt-in apps or compromised devices). Because the IPs belong to legitimate ISPs, they defeat naive IP blocklists.
• Datacenter proxies — relay through IP ranges owned by cloud or hosting providers. Cheaper than residential proxies, but easier to detect because their ASNs are well known.

Why bots use proxies

For attackers, proxies are how you turn a single noisy script into traffic that looks like many independent users. A scalping or credential-stuffing operation will typically rotate through a pool of thousands of proxies so that no single IP address generates enough requests to trip rate limits or account-lockout rules. Residential and mobile proxies are particularly prized because:

• Their IPs belong to legitimate consumer ISPs, so geo and ASN filters wave them through.
• Each IP usually carries a clean reputation — it hasn't been flagged by abuse feeds.
• Rotation can happen on every request, so the origin sees what looks like one-and-done traffic from new users.

The result is that simple IP-based defences (block this IP, rate-limit that ASN) catch only the laziest bots. Anything serious needs to combine network signals with browser, TLS and behavioural signals.

How Procaptcha handles proxy traffic

Prosopo's access control rules treat proxy detection as one signal among several, not as a kill switch. A site can configure rules that allow, challenge or block traffic based on combinations of IP reputation, ASN, geolocation, JA4 TLS fingerprint, and behavioural analysis. That layered approach matters because legitimate users sometimes browse via a VPN or corporate proxy and shouldn't be blocked outright, while sophisticated scalpers rotate through proxies specifically to look legitimate. By correlating multiple signals rather than relying on any single one, Procaptcha keeps real users moving while raising the cost of proxy-driven bot attacks.