Who is spying on my texts?

Yesterday morning at home I got a call on my cellphone regarding a broken window (not at my house but in another building), after which I exchanged a number of text messages on the subject.

Imagine my surprise when I turned on my computer a few minutes later to visit one of my favorite websites, and up popped an advertisement for an emergency window replacement service. I’m sure this was no coincidence, as I’d never seen this advert before.

How, I wondered, could the Internet suddenly “know” that I was in conversations about a broken window, unless it was somehow spying on my cellphone traffic and linking it to my computer? I think it’s because I have a cellular signal booster that routes my cellphone traffic through my internet connection, and/or because my cellphone connects to the WiFi in my house. Either way, it means that someone, probably my cable/internet provider, is monitoring the traffic going to and from my IP address, looking for keywords and selling the information to advertisers. (They could also be listening in on my phone calls, which, although scarier, seems less likely as it is technically harder.)  It would be interesting to devise an experiment to test this hypothesis….