''If you think you're going to get anything from my mother, good luck,'' John Hancock said in a rare statement on Friday night, referring to potential kidnappers.

Mr Hancock, who along with his two sisters is taking legal action against his mother for control of the family's $20 billion fortune, spoke after Mrs Rinehart said she feared her five grandchildren were at risk of kidnapping, murder and terrorism because of the case's profile.

Emails and court documents released by the NSW Supreme Court on Thursday showed she wanted suppression orders over the case because she was concerned ''for the safety of her children, her grandchildren and herself'' due to media coverage of the ongoing family feud.

A security risk assessment report suggested the family would be at risk from ''criminals and deranged persons'' if details were released about the battle over a family trust.

Mr Hancock, his wife and children, who live in Thailand, could be targeted by ''organised criminals operating in Thailand including the Russian mafia'', the report said.

Mr Hancock, 36, told The West Australian on Friday that Mrs Rinehart was worsening the security issue by drawing attention to the family.

The Australian Financial Review reported yesterday that the man once touted to take over running the family company, Hancock Prospecting, had resorted to day-trading on the sharemarket and made a $119,000 profit in five months.

''I can support my wife and children in a modest manner from the work I do but I can't provide the level of funds required to deal with security issues - real or imagined - associated with being the son of a woman worth more than $20 billion,'' he said.

''When my mother buys a few hundred million dollars worth of Fairfax [shares], it's going to draw some attention. But she won't share a penny to help protect her grandchildren from the risks she … is creating.

''Even the production of this expensive report causes more problems … what more can I do than communicate to any kidnappers out there - over my dead body and you will be wasting your time anyway. If you think you're going to get anything from my mother, good luck.''

The Sun-Herald left messages seeking comment from Mrs Rinehart with her company's communications director, Cheryl Edwardes. A message was also left on the home telephone of a senior Hancock Prospecting executive, Jay Newby.

Mr Hancock is involved with his two sisters - Hope Welker and Bianca Rinehart - in the legal battle to have their mother removed as head of the family trust.

Last year, weeks before taking Mrs Rinehart to court, Hope Welker emailed her mother requesting money to hire a bodyguard. ''I'm down to my last $60,000 and you're only paying my husband $1 a year,'' she wrote. The security report said Mrs Welker and her children could be at risk if the suppression order were lifted.