The Internet has turned the advertising world on its head. As the media has changed, so too has IT at the $144-million agency.

A few years ago, Greg Folsom, vice president and director of IT at ad agency Arnold Worldwide, decided to test the company's Internet monitoring software by blocking access to porn sites. About five minutes later, his phone rang: Someone was complaining that he couldn't view X-rated material on his browser -- apparently necessary research for the creative process. Folsom turned the porn back on.

"It's a great place to work," Folsom laughs. "You can justify anything."

Boston-based Arnold is one of the top 20 ad agencies in the U.S., known for its innovative campaigns for clients such as Volkswagen and Jack Daniel's. But Arnold is also a midmarket company in a highly competitive sector beset by whirlwind change as technology upends traditional advertising channels.