A VPN detection API is a tool that allows businesses to identify when a user is connecting to their website via a proxy or other type of VPN connection. This can help businesses prevent fraudulent activity, enforce geo-blocking, and strengthen their KYC (know your customer) processes. There are a number of different VPN and proxy detection tools on the market, some free and others paid.

Using a VPN or proxy is a great way to stay anonymous online, and there are many legitimate uses for them. However, there are also some risks associated with using a VPN, including the risk of data being exposed by a “VPN leak.” A VPN detection tool can help businesses detect these leaks and prevent users from visiting sites that might expose their personal information.

While detecting VPN connections is not necessarily a bad thing, it’s important to keep in mind that these connections are often used for illegitimate purposes. For example, cybercriminals can use proxies to spoof their location, hide their identity, and access restricted content. Fraudsters can also use VPNs to bypass security measures and get around geo-blocking and filters. In addition to detecting VPN usage, many VPN detection tools can also detect other types of illegitimate activities, such as spamming, account creation, and other kinds of fraud.

In order to detect VPN or proxy use, these services generally examine a web request and check for certain headers. The Via header in particular is often a giveaway, as it indicates that the HTTP or HTTPS request is being forwarded through a proxy server. Other common headers that can indicate a VPN or proxy include the Strict-Transport-Security (STS) and Content-Length-Lens (CLS) headers.

These services also typically look for DNS-based blackhole lists (DNSBLs) that list IP addresses known to be associated with proxies and VPNs. Additionally, they can look for a variety of other data points, including the number of recent requests and whether the IP address is listed in any malware or hacker databases.

Some of these services offer a free tier with up to 1000 requests per day, while other services require a subscription. One of the most popular is GetIPIntel, which has been around for over 6 years. Its API offers instant detection of anonymous proxies, VPNs, TOR exit nodes, and residential proxies. It also provides additional verification of these connections, including looking for data centers and hosting/servers.