SAN FRANCISCO — A federal judge has picked a coalition of five plaintiffs firms to oversee litigation targeting Yahoo Inc. over its massive data breaches.

U.S. District Judge Lucy Koh of the Northern District of California on Thursday named John Yanchunis of Morgan & Morgan lead counsel in multidistrict litigation brought on behalf of the billion-plus Yahoo customers affected by the breaches and appointed lawyers from four other firms—Milberg; Robbins Geller Rudman & Dowd; Casey Gerry Schenk Francavilla Blatt & Penfield; and Lockridge Grindal Nauen—to the plaintiffs’ executive committee. The lawyers are based in New York, Florida, Minnesota and California.Koh picked the five-firm coalition over three individual firms—Kaplan Fox & Kilsheimer, Kessler Topaz Meltzer & Check, Susman Godfrey—who vied for the lead counsel slot independently and criticized the larger group’s structure as expensive and unwieldy.