When Joanna, 25, was still dating her live-in boyfriend Ted, she would wait till he fell asleep before doing her regular deed: Checking his smartphone for signs of a "double life".

It would be a quick two-minute task ("I couldn't risk him catching me in the act"), but her search was thorough. "I would go through his Facebook and Pinterest account, SMSes, notes, Safari browser history, Whatsapp messages… Anything that involved data input from him," admits the advertising executive.

She would also note which Facebook friends he interacted with the most, scanning through the private messages they sent him.

Even though he often changed his phone's passcode, she always figured out what it was "by watching his fingers whenever he typed it in", she adds.

Joanna admits she snooped on Ted right at the start of their relationship because he had a "roving eye". While she had never caught him cheating, he would frequently check out other women when they were out. She also had a "gut feeling" he wasn't telling her everything about his life.

Joanna finally discovered that Ted had been keeping in touch with a former flame even though he denied it at first. He was also telling others he was "single", even though he'd been dating Joanna for close to a year.

These revelations pushed her to end their relationship recently after less than a year of dating.

Read the full story here.

Click on the thumbnails for tell-tale signs of a cheating partner.