Detecting VPNs through Latency Measurements: An In-Depth Analysis

Detecting VPNs through Latency Measurements: An In-Depth Analysis
  • Published: March 10, 2023

Virtual Private Networks (VPNs) are widely used to bypass geographic restrictions. However, there are situations where organizations or governments may want to detect and block VPN usage. One such method of detection is by measuring latency. In this blog post, we'll delve into the intricacies of latency and explore how it can be used to detect VPNs.

Understanding Latency

Latency, in the context of computer networks, refers to the time it takes for a packet of data to travel from the sender to the receiver. It is usually measured in milliseconds (ms) and is influenced by various factors, including the physical distance between sender and receiver, the number of intermediate nodes, and the efficiency of the network equipment. Latency can be measured using various methods and tools, the most popular being a ping. A ping - technically refered to as a Internet Control Message Protocol (ICMP) echo requests - measures the round-trip time (RTT) between a source and a destination. The RTT, which includes both the time taken to send the request and the time taken for the response to arrive.

VPNs and Latency

When a user connects to a VPN, their internet traffic is routed through an encrypted tunnel to a remote VPN server. This process adds extra steps to the data transmission, leading to an increase in latency. The additional latency depends on the VPN server's location, the encryption method used, and the performance of the VPN service itself.

Measuring Latency to Detect VPNs

First, establish a baseline latency for users with a known geographic region that are known not to be connected to a VPN. This can be done by measuring the latency between the client and a known server, such as a popular website or a server within the organization. By doing this, you can understand the typical latency range for non-VPN users in a specific location.

Second, continuously monitor the latency of users within your network. This can be done using network monitoring tools, which can analyze network traffic and measure latency between different nodes.

Look for instances where the measured latency is significantly higher than the established baseline for a specific geographic region. This could indicate that a user is connected to a VPN, as VPNs generally add extra latency to network connections. To increase the accuracy of VPN detection, it's essential to correlate latency measurements with other data, such as IP addresses, geographical data, DNS requests or browser fingerprinting.

Limitations and Considerations

While latency measurements can be a useful tool for detecting VPNs, it's important to note that this method has limitations. High latency does not always imply VPN usage. Network congestion, poor-quality connections, or other factors can also cause increased latency. VPNs with servers located close to the user may not exhibit a significant latency increase, making them harder to detect using this method.

Measuring latency can provide valuable insights into VPN usage within a network, but it is difficult to implement and very unreliable. As VPN technology evolves, so must the methods employed to detect and manage them. A more reliable solution is using the Focsec's VPN Detection API will give more accurate results. Focsec also detects Proxies, TOR users and bots.

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