Angela Ricketts, the wife of an Army officer in Colorado, was startled by the message that popped up on her Facebook account last week.
"Dear Angela! Bloody Valentines Day!" the message began. "While your president and your husband are killing our brothers in Syria, Iraq and Afghanistan we're coming for you."
It went on: "We know everything about you, your husband and your children and we are much closer than you can imagine. You'll see no mercy infidel!"
The message was sent from an account called "CyberCaliphate." It claimed to be on behalf of "IS," or Islamic State — also known as ISIS.
"I'd be lying if I said it didn't frighten me," Ricketts said. "It had my full name and was very specific."
Ricketts, the author of a memoir titled No Man's War: Irreverent Confessions of an Infantry Wife, was one of five military spouses who received the threatening messages. All are prominent advocates for military families who have been quoted in the news media.
Ricketts and Lori Volkman, wife of a Naval Reserve officer, said in interviews that they had spoken with the FBI, military investigators and local police. They said authorities were trying to determine who sent the messages and whether they had any contact with ISIS.
They provided a screen grab of a similar message apparently sent last week to first lady Michelle Obama's public Twitter account: "Bloody Valentines Day, .Michelle Obama! We're watching you, your girls, and your husband. .CyberCaliphate."
A White House spokeswoman declined to comment. Alice Heller, an intelligence analyst for the FBI in San Francisco, said she could not comment on active investigations.
"The FBI takes all threats from ISIS or those claiming to support ISIS very seriously, and responds appropriately," Heller said.
Chris Grey, a spokesman for the Army Criminal Investigation Command, said investigators were "not confirming names or circumstances involving specific individuals to help prevent them from being revictimized."
Ricketts and Volkman say they have received protection from police and have taken extra security measures at home and school.
The hacker or hackers penetrated the Twitter account of a military spouse who runs a military-oriented nonprofit, Volkman said. The hacker then used her contacts to send Twitter and Facebook messages to at least four other spouses.
Volkman said the spouses soon realized that all five had been quoted in a January news report about the hacking of a U.S. Central Command Twitter account by someone claiming to represent ISIS. "AMERICAN SOLDIERS, WE ARE COMING, WATCH YOUR BACK. ISIS," wrote the hacker, who displayed an ISIS-like logo.