When David Koch first saw an unauthorised online advert featuring his face, he was horrified.

Koch, the former host of Sunrise and a financial expert, knew that someone had taken his photo and placed it in an advert, using it as bait to scam the public and steal money.

Koch took to social media to alert his followers to the illegitimate advertisement, but that was clearly not enough.

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In a special 7NEWS Spotlight investigation, the team lift the lid on the multi-billion-dollar scam industry in which fake advertisements featuring well-known celebrities have been used to con more than 600,000 Aussies.

“It’s devastating because it’s my reputation on the line,” says Koch.

“And these scams are so good, they’re so believable that people who trust me look at me and say, ‘Wow, I’m getting some comfort out of what this bloke is saying,’ and then are ripped off by some scammer from overseas.”

Koch is desperately trying to stop this criminal act.

“I’ve reported it to the ACCC and ASIC. I’m part of an ACCC case against Meta at the moment surrounding these scam ads,” he says.

And while Koch is doing all he can behind-the-scenes to stop the cybercriminals in the act, he’s now seen first-hand the victims of these crimes.

During the 7NEWS Spotlight investigation, Koch meets Allison, who lost $250,000 when she invested her money in what she thought was a reputable company, fronted by who she believed to be the former Sunrise host. As an avid Port Adelaide supporter, she trusts Koch, who is also the Chairman of the football club.

“Port Adelaide members are all part of a big family,” says Koch. “And the fact that these scammers use my association with the club to prey on members is just abhorrent.”

Following the loss of her savings, life is tough for Allison. After a 40-year career, she is living on a very tight budget and is on a payment plan so she can stay as a member of the AFL club she loves.

After learning of her story, Koch himself has stepped in and ensured she has lifelong membership.

“It’s the least we can do,” says Koch to Allison. “Because, football has got to be your haven.”

Allison is one of many Australians featured in the 7NEWS Spotlight investigation, and reporter Sarah Greenhalgh believes millions of dollars have been illegally stolen.

“The scammers successfully prey on these people’s unique vulnerabilities and the victims’ lives have changed forever as a result,” she says.

Watch 7NEWS Spotlight: Social Scammers

If you need help in a crisis, call Lifeline on 13 11 14. For further information about depression contact beyondblue on 1300224636 or talk to your GP, local health professional or someone you trust.