The FBI has long been known for its straightforward “Just the facts, ma’am” approach, an image reinforced by Director Robert S. Mueller III’s stoic presence and reluctance to court the media.

But in a sign that the online revolution is infiltrating that most traditional of agencies, the bureau unveiled Monday a publicity campaign featuring public service announcements in 14 cities and billboards in New York’s Times Square, along with a heavy dose of Facebook, YouTube and Twitter.

The purpose: to help agents catch James “Whitey” Bulger, the notorious Boston mobster and government informant who vanished 16 years ago.The 81-year-old is charged in 19 killings and has been on the FBI’s “Ten Most Wanted Fugitives” list since 1999. Bul­ger, an inspiration for the movie “The Departed,’’ has been called “Boston’s boogeyman” and has supposedly been “seen” in nearly every state and on at least five continents.

To get a better fix on Bulger, the FBI is focusing on his longtime girlfriend, Catherine Elizabeth Greig, a fugitive charged with harboring Bulger. Agents devised a media campaign focusing on the couple’s relationship and pointing out Greig’s “physical characteristics,’’ the FBI said in a news release.

Although agents have used publicity to target fugitives before, Richard DesLauriers, special agent in charge of the FBI’s Boston division, said in an interview that the breadth of the new campaign is “relatively unique.’’

“We’re looking for that friend, co-worker, neighbor, hairstylist, manicurist who might recognize her,’’ said DesLauriers, who declined to provide specifics about the investigation.

The level of detail is classic FBI. Greig, 60, likes beauty salons, loves animals and “is likely to have well-kept teeth because she previously worked as a dental hygienist,’’ the release said.

Public service announcements will start airing Tuesday in cities where Bulger or Greig have ties, during shows with high female viewership. More information can be found on the FBI’s Web site and its Facebook and Twitter accounts.