Sara Payne said she was "very distressed and upset" as she spoke for the first time of being caught up in the News of the World phone hacking scandal.
Ms Payne, who worked closely with the Sunday paper to campaign for tougher child protection laws, vowed to challenge "the bad apples head-on".
And in her first public statement since news broke that she may have been hacked by private investigator Glenn Mulcaire, she vowed to play a proactive part in preventing it happening again.
In a statement to the Press Association, Ms Payne said: "I am, as you can imagine, very distressed and upset by the news that my details have been found on Mulcaire's list and would like to thank everyone for their kind words of support.
"I can confirm reports that I was given a phone by the campaign team and that my voicemail was only activated after my first aneurysm.
"Notwithstanding the bad apples involved here, my faith remains solidly behind all the good people who have supported me over the last 11 years. I will never lose my faith in them.
"My way would be to challenge the bad apples head-on, learn from the facts of the matter and be a proactive part of stopping this from happening again.
"I'm away with my children and family at the moment. For their sake and for the sake of the ongoing investigation, I can make no further comment at this time."
Ms Payne spoke out hours after Mulcaire's legal team said he acted "on the instructions of others".
His lawyers strongly rejected suggestions that he "unilaterally" hacked into voicemails of victims without the newspaper's knowledge.