When sports stars get abused on social media, they are often advised to turn the other cheek.
But for some athletes, ignoring comments that can range from insults to even death threats is simply not an option.
Take two-time America's Cup winner Jimmy Spithill.
When the Australian led Oracle Team USA to a remarkable come-from-behind win in the 2013 America's Cup, he began receiving abusive and threatening comments online.
Some of it was directed at his young family, which prompted Spithill to seek the help of two private investigators from New Zealand and an imposing Bulgarian, who found the culprit and made him stop.
"When you grow up being bullied, you can just sit there and take it," Spithill, a father of two young children, told CNN recently by phone from his home in Los Angeles. "Or you say, 'No, I'm going to do something about this.'"
The Australian was born with a limp, which led to him being bullied in high school, an experience he wrote about in his book "Chasing the Cup: My America's Cup journey."
"I wouldn't have cared if it had been aimed only at me," he wrote, "... but when this guy using an alias started writing on Facebook the address of our houses in San Francisco and New Zealand, together with photos, and going on to make terrible comments about my family, it had gone too far: it was abusive and menacing.
"This was not freedom of speech -- it was a really nasty vendetta aimed at my family and me."
A Kiwi friend, whose father and brother were private investigators, came to the rescue.
"They didn't muck around," Spithill wrote. "Within a few hours they were able to pinpoint the perpetrator: he was a Kiwi living in London."
'Not expecting a knock on the door'
The men then enlisted what Spithill described as a "rather tall, somewhat imposing Bulgarian gentleman," to pay the offender an unexpected visit.
Within an hour of the Bulgarian knocking on the door, Spithill's team was given a guarantee by the offender that everything he had posted would be deleted straight away.
"If you're at home, sitting in your cupboard on a laptop, you can be Superman," Spithill said from Los Angeles. "But obviously they're not expecting a knock on the door.
"I actually have no problem with someone wanting to have a go at me, I'm a big boy and can look after myself," Spithill added.
"But when it involves children or people that can't defend themselves and they're vulnerable and they are your own children, then you've got a real problem with it."
Why tennis player calls out internet trolls
As one of the world's top tennis players, US Open finalist Madison Keys has had her fair share of insults, racist and sexist comments and even death threats from disgruntled gamblers after matches on social media.
Last year, Keys became the ambassador for FearlesslyGIRL, a North American leadership organization dedicated to empowering young women. The 22-year-old also recently helped host the biggest-ever anti-bullying school assembly in the US.
Although the tennis authorities advise players not to engage with the perpetrators of online abuse, Keys said she regularly calls out nasty comments or threats.
"The official line is you shouldn't do it, but at the same time it empowers these people to say whatever they want and nothing is going to get done," Keys said, in an interview at the Wuhan Open in China earlier this year.
"Also, if you call them out, the number of people that can report them goes from one or two to thousands."
Keys called on social media companies including Twitter and Instagram to step up the fight against cyberbullying and users making menacing, racist or sexist comments on their platforms.
"They need to do more and there should be more protection," she said. "Sometimes I'll report something but just because they didn't technically threaten your life, they can't shut it down.
"There should be stricter rules. I understand companies not wanting to take the freedom of speech away, I get that and I appreciate that. But there is definitely that grey area that doesn't always get policed correctly."
When asked for a response to Keys' comments, a Twitter spokesman pointed to more than 20 changes the social media platform has made this year to its product, policies and processes to make its users safer online.
"We're now taking action on 10 times the number of abusive accounts every day compared to the same time last year," the spokesman said.
In the last four months, Twitter has removed twice the number of new accounts set up by repeat offenders after their old accounts were suspended for violations.
Instagram declined to comment about the experiences of Spithill and Keys.
However the social media company, which is owned by Facebook, says in its community guidelines it wants "to foster a positive, diverse community," has a team of reviewers that work 24/7 to check and remove violating content or accounts. It also recently launched an automatic comment and spam filter to block certain offensive comments and spam on posts and in live video in a variety of languages.
On Tuesday, Facebook said it was releasing"new tools to prevent harassment on Facebook and in Messenger -- part of our ongoing efforts to build a safe community."
"We already prohibit bullying and harassment on Facebook, and people can let us know when they see something concerning or have a bad experience," said the social media company.
"We review reports and take action on abuse, like removing content, disabling accounts, and limiting certain features like commenting for people who have violated our Community Standards."
Impact on young children
As the father of two young children, Spithill is deeply concerned about the impact cyberbullying can have on young kids.
"I think that's one of the biggest challenges," he said. "With physical bullying it's obvious the kid is having a big problem because they are coming home with a black eye. That whole mental side and this online bullying, it's a real worry. Because how do you know?" he added.
"My kids are only six and 10," Spithill said. "We keep them away from a lot of the technology, and just keep them involved in group activities and stuff. But it's just one of those balances.
"I was talking to a mate the other day, and the question was, are we better off with or without social media?" Spithill said.
"I do it all because it is part of the job now, to connect, and people want that commercial return and stuff.
"But the negativity that can come with these online social media applications, my take on it is that we're better off without it."
Spithill hired two investigators who tracked down man who threatened him online
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