Ferry, who is currently the director of investor relations and corporate affairs at Dixons Carphone, will succeed Torrens, who will step down from the board later this year.
Before working at Dixons, she was a retail analyst at Merrill Lynch and prior to that an audit manager at PwC, where she qualified as a chartered accountant.
Sir Charles Dunstone, executive chairman, said, "On behalf of the board, I would like to thank Iain for his hard work over the last few years. He has been a valued member of the TalkTalk team and the board and we all wish him well for the future.
“I am also delighted to welcome Kate to TalkTalk. As we continue our journey under the new leadership team and with a refocused direction, Kate brings a wealth of experience to the role. Her skills will work really well at TalkTalk and we're looking forward to working with her as we focus on delivering our new and exciting plan for the business."
The company said the exact dates of the appointment have not been confirmed.
TalkTalk was hit with a record fine of £400,000 last year after the Information Commissioner’s Office found that security failings at TalkTalk allowed a cyber attacker to access customer data “with ease”.