Mary Ellen Callahan, chair of new privacy practice at Jenner and Block, previously worked as chief privacy officer at the Department of Homeland Security. (Jeffrey MacMillan/JEFFREY MACMILLAN)

Jenner & Block, the Chicago-based law firm with 80 attorneys in the District, is creating a privacy and data protection group under the leadership of Mary Ellen Callahan, the former chief privacy officer for the Department of Homeland Security.

Privacy and data protection is one of the booming areas for law firms, as companies increasingly grapple with how to move sensitive data onto Internet-based systems and keep their information secure. Privacy lawyers also advise businesses that deal directly with consumers on the legal bounds of collecting and using data about customers, such as spending habits and Web surfing patterns. Although many Jenner & Block lawyers have done privacy work, this is the first time the firm is formalizing the practice group.

The privacy group is to complement the firm’s existing practices, which work with companies in the media, entertainment, retail and government contracting sectors.

Callahan, who was appointed to her previous post by President Obama in 2009, will focus on information governance and security — which includes advising companies on national security-related issues that arise when defense contractors and the government share confidential information.

Before joining Homeland Security, Callahan was a partner at Hogan Lovells and an adviser for Obama’s 2008 presidential campaign, where she helped the campaign form positions on consumer privacy and technology issues.

Many major law firms in Washington — including Venable, Hogan and Covington & Burling — have large and established privacy practices, but Callahan said the draw of joining Jenner & Block was the opportunity to build a practice on her own terms.

“Having run my own office for three and a half years, I wanted to do something new,” she said. “I do think the market is ripe for this. There is a real growth opportunity in privacy practices, not just in D.C. but nationwide. People are understanding this isn’t just about, ‘Can I send an e-mail?’ It’s more about, ‘What can do with information, and how do I move from legacy databases to the cloud?’ ”

Callahan plans to hire lawyers to join her group by early next year. She is particularly interested in attorneys who have served in the Federal Trade Commission, and attorneys who have represented companies in FTC investigations.

“I’m looking to build a pretty robust practice,” she said. “It’s probably a two- to five-year prospect to have this be to the caliber that I want it.”