Does my ISP know if I use a VPN? by Westley Julio
Answer by Westley Julio:
If they want to know they would be able to figure it out.
Your ISP knows what network(s) you’re connecting to. If the network you’re connecting to belongs to a known VPN provider, they know you’re using VPN services.
Even if the ISP doesn’t know that a specific destination is a VPN provider, if a large portion of your traffic goes to/from this network, it can be inferred that you’re likely using VPN technologies. A ‘normal’ use pattern would be a customer sending to and receiving from a variety of places. VPN use consolidates destination and data transfer stats.
VPN use could also be inferred from other clues. For example, browsing a website usually involves a DNS request (if uncached), downloading a page of content, pausing, downloading another page, pausing, etc. Video streaming would look like downloading high volumes of data for an extended period of time then stopping. The VPN will hide the data, but doesn’t hide the statistics that can be gathered on usage patterns in terms of timing, volume, etc. Granted, they would see aggregate statics between all uses. This information wouldn’t likely be conclusive and would become increasingly not useful for this purpose the larger the client’s organization is or becomes.
Your ISP could also capture packets that traverse their network and might be able to observe certain telltale VPN related handshakes taking place.
Essentially, your ISP has access to information about you that isn’t available to the general internet. Probably the most compromising of which, for this purpose, is that they can see how your use changes over time.