Last week, a family from Portland, Oregon chose to disconnect their beloved Amazon Alexa, despite relying on it for lights, security and various helpful duties around the home. This was due to their device reportedly recording a conversation then sending it off to a contact without their knowledge.

Fortunately, the private chat was only about flooring – the recording sparked by an accidental usage of Alexa’s “wake word” in conversation.

Not all private conversations cover topics as mundane as home improvements, however, and it’s an incident that has fed into a particular growing paranoia concerning our modern gadgets and gizmos: the idea that these devices are always listening to us.

Initially, this may seem more in line with a dystopian film than our current reality, yet it’s not an entirely unjustified fear. Let’s say you’re talking about getting a new car. You discuss a certain brand you think you may like, but it is ultimately just something you’re mulling over rather than a definite commitment. Fast forward a day when you’re scrolling through your Facebook feed and you suddenly get an advertisement for that very car.

An isolated incident like this may appear to be nothing more than a coincidence, but all you need to do is take a step into the world of Reddit, an online discussion site, to find hundreds of other examples of this happening.

So is Alexa simply an early model of a future HAL 9000 – the rogue super-computer from the film 2001: A Space Odyssey – that will manage, control and sell on our entire lives for shadowy tech conglomerates’ nefarious purposes? The developers behind apps and devices you’ve agreed to give access to your data are certainly cagey about what they have and what they don’t, but none would ever admit to ongoing surveillance of their customers.

The truth is, you very likely aren’t being listened to by an actual human being – but firms are certainly applying powerful algorithms to look for patterns in your searches and behaviour to determine information that could be commercially useful to them.

The problem remains that such audio data can reveal much more than many people imagine. Your phone mic recording ambient noise could determine if you’re in the pub or the shower. Background voices could reveal who you’re with. Measuring noise levels can also reveal when you’re asleep, how long you sleep for and whose address you’re sleeping at. A very accurate picture of you and your everyday is not difficult to create.

However, Grant Gibson, deputy managing director of the Glasgow-based digital marketing agency Bright Signals, is presently not inclined towards technological paranoia.

He said: “There’s no doubt that these ads can be spookily timely, but there’s no evidence that they’re listening in to conversations to achieve that.”

Before we sigh with relief, he also claims that technology can certainly be used against us in questionable ways. “There are plenty of other dubious ways that apps can track your interests and associations. By tracking your location and IP address, apps can infer which shops, pubs and health clubs you visit and, thanks to the network effect of everyone having a smartphone, they can even work out who you’re meeting. Connect to your car’s Bluetooth and they can track the make, model and age of your car. And, by combining data with other digital providers, can build a frighteningly complete picture of your habits.

“Most modern gadgets from TVs to smart watches have the physical capability to listen to you. And thanks to the internet, it’s trivial for them to silently send that audio around the world. No matter how ethical the manufacturer, these gadgets have the potential to be co-opted by third parties to share your private content.

“For many people, myself included, it’s an uncomfortable bargain that we make in exchange for being able to summon up any movie or song, in any room, without having to lift a finger.”

Dr Mark Leiser, of the University of Leicester, claims that most of the advertisements we do get are based on browsing history and shared documents, like Word or PowerPoint, being scanned for keywords that can tie into endorsements, rather than us being actively listened to.

Leiser assures us that if companies like Facebook were listening to all of our conversations, they’d be trawling through a hurricane of data – devoting a lot of effort just to promote our dream car. Despite tech companies continual assurances, apprehension over these devices’ omnipresence is how our lives looks certain to remain – especially as the sophisticated technology powering our devices evolves and matures.