ISPs use a variety of techniques, such as deep packet inspection.
Many ISP support centers use commercial software [1] to display a detailed analysis of website usage whenever a customer calls in for support.
This includes the top websites visited, how much data was transferred for each site (yes, including those of a more salacious nature), the number and type of devices inside a home, nearby Wi-Fi networks, etc. [1]
This information can then be queried and used used for marketing purposes at the subscriber level (or to individuals within a dwelling).
Many ISP support centers use commercial software [1] to display a detailed analysis of website usage whenever a customer calls in for support.
This includes the top websites visited, how much data was transferred for each site (yes, including those of a more salacious nature), the number and type of devices inside a home, nearby Wi-Fi networks, etc. [1]
This information can then be queried and used used for marketing purposes at the subscriber level (or to individuals within a dwelling).
[1] https://www.calix.com/content/calix/en/site-prod/library-htm...
[2] https://www.calix.com/compass/access-analyze.html
[3] https://www.calix.com/compass/consumer-connect-plus.html