For wifi networks that are operated by small businesses, they often ask the user to register a name and accept a TOS agreement before they can start browsing. And later those networks will remember this device and wont ask for information again. I'm wondering how they can tell it's the same device. Is it the mac address, or is there some kind of certificate stored on your device? I tried spoofing the mac on my wifi network the other day, but the network still remembered me. In other words, what are the ways the owner of a network can identify the devices connected to it?


Generally, it is done by MAC address of the WLAN Card.

In theory, though, the captive portal could also store a cookie in the web browser used to authenticate against it to quickly re authenticate against the webpage without the user having to type in their name/agree to the terms of use again.

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    Some enterprise APs also have client software that uses other forms of authentication. Some of it is proprietary, some are configured via other means - Group Policy, SSL/TLS certificates, or hardware identification. It really depends on what the AP is capable of. – user201262 Feb 14 '18 at 16:42
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    @Moses, that is true, and also Windows can use certificates for authentication if 802.1x authentication is used, but that's not usually for guest wireless access. – Allen Howard Feb 14 '18 at 17:37

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