It's a chilling and deeply disturbing trend and incidents appear to be growing at an alarming rate.
In the sinister world of domestic abuse and coercive control, perpetrators have a new way of terrorising their victims – technology – and figures show tech abuse is becoming a stalker’s weapon of choice.
Research by the Tonight programme shows an 1800% increase in alleged cyber stalking offences between 2014 and 2018.
It can be a subtle as turning the heating up or down, switching lights on and off, remotely - or as blunt as hurling abuse over social media.
Extreme examples can see stalkers steal bank account and credit card details, use online passwords to control social media profiles and has sometimes seen victims killed by their stalker.
One victim, Natalie, tells presenter Julie Etchingham how her ex-husband sought to control her life through technology.
"He’s very convincing and charming," she says. "So it’d be like ‘Oh, do you want to use this? It will be much easier...’
"So it kept a record of all my messages on the computer, but because he was also using the computer, he could reply and he could see when messages had come in."
He soon uploaded an app to her mobile that could check in and get a snapshot of where she was at all times.
She adds: "It would sit there in the background and it would take a picture and send it to him…and coordinates of exactly where I was."
She says he also installed cameras in the home to follow her around the house, spying on her in various rooms.
Natalie says that while police officers are experienced in dealing with 'traditional' cases of domestic abuse and domestic violence, cyber stalking and using technology to control someone's life is new to them.
"The manipulation, you know, the psychological programing it has a huge effect," she says, "because it's relentless. It's a constant window into your life. It's a constant way of checking where you are."
In the last year, domestic violence charity Refuge has documented over 4,000 people who said they’ve experienced tech abuse - that's three-quarters of people who have used their services.
In 2017, an inspection into the way police dealt with stalking cases found they often failed to recognise stalking, and would incorrectly log it as harassment.
This mistake can be costly as the Suzy Lamplugh Trust explains: "It's really dangerous for police to be treating stalking cases as harassment because what essentially happens is that the key component of stalking, that fixation and obsession doesn't end up being addressed."
Another victim, Lara, tells Julie how her controlling partner used to take over the heating of the home they shared - through his phone - turning it down whenever he wasn't there.
"I came for a home, but I ended up in a house that it was like a prison, his prison," she says.
"It took couple of weeks for me to understand that he was turning the heating off from afar.
"I felt scared but I wanted something just to prove what he was doing, because I thought I was going crazy."
While most stalking cases involve current or former partners, technology is also providing a path for more random, anonymous stalkers to thrive; preying on others they have never met other than through social media.
Writer Paul was deluged on Twitter with homophobic abuse: "At the height of it, I was getting sort of 20, 30, 40, 50 tweets a day.
"Whenever I heard my phone pinging my first feeling was that sinking feeling in your stomach and that sort of cold dread of what's it going to be now?"
While he blocked the anonymous abuser, it didn't stop. Anyone he came into contact with through social media could find themselves receiving abuse.
He eventually reported the abuse to police and a woman was later given a suspended two-year jail term and issued with a restraining order.
In 2018, MASIP (Multi Agency Stalking Intervention Programme) was launched and aimed to improve responses to stalking across the criminal justice system and the health sector through rehabilitative treatment of stalkers with units in London, Hampshire and Cheshire.
Detective Inspector Lee Barnard, who runs the London unit, tells the programme that he believes it’s increasingly clear tech plays a big role in stalking cases.
He says: "More than any other offence type that I've investigated in my service, stalking is probably the most impacted by technology.
"If we're in the business of tracking human beings, there's a huge array of technological devices out there, apps, software that can assist with that."
Tech Abuse: Stopping the Stalkers – Tonight airs on ITV at 7.30pm
If you think you’re being stalked or cyber stalked, you can find help here:
National Stalking Helpline – 0808 802 0300 or complete a form here: https://www.suzylamplugh.org/forms/national-stalking-helpline-enquiry-form
Refuge (National Domestic Abuse Helpline) – 0808 2000 247 or email email@example.com
If you want to secure your devices, you can do it here:
Cyber Care – 07496 955219 or firstname.lastname@example.org