They fear that since the Royal Wedding, when Pippa's rear grabbed worldwide attention, she has become vulnerable to attack.
And unlike her sister Kate, the 27-year-old is not guarded by Royal protection cops. Her millionaire dad Michael, 61, and mum Carole, 55, are now looking at buying a £95,000 bomb-proof BMW or Audi.
It would have bullet-proof windows and still be able to drive if the tyres are shot out.
The Middletons discussed potential threats with Prince William's top bodyguard. The main concern is that an obsessed fan or terrorists will try to get at Pippa.
It is believed she already carries a panic button linked to cops. Similar buttons are also at the family home in Berkshire.
A source said last night: "Carole and Michael have taken a raft of measures following advice from one of William's most trusted bodyguards.