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 or ISIL.
"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 Navy 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 Islamic State.
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 Islamic State. "AMERICAN SOLDIERS, WE ARE COMING, WATCH YOUR BACK. ISIS," wrote the hacker, who displayed an ISIS-like logo.
The messages the spouses received were accompanied by the same logo, of a man in a checkered kaffiyeh next to the ISIS flag, with the title "CyberCaliphate." The messages were first reported by Military.com, where one recipient, Amy Bushatz, is the managing editor. Bushatz wrote on her blog, SpouseBuzz.com:
"I want to face this whole situation with a resolute jaw and a loud 'being afraid means the terrorists win.' I'm not the type of person to live in fear or change my life just because some person on the Internet wants to scare me."
After the hacking of U.S. Central Command last month, some military spouses said they tightened security on their social media accounts or shut them down. Some removed photos of their children.
The Defense Department offers tips for protecting social media accounts at http://www.defense.gov/documents/WEB_Guide_to_Keeping_Your_Social_Media_Accounts_Secure_2015.pdf
Ricketts said that when she first saw the threatening messages on her accounts last week, her "first thought was, 'Oh, creepy.'
"Then I realized, 'Oh, he friended me too.'"
On Valentine's Day, Ricketts said, she received a second Facebook message showing a photo of a masked man brandishing a large hunting knife. None of the other spouses received a second message, she said.
Volkman said she saw the messages on her accounts while she was in the kitchen with her children at the family's Washington state home. Volkman, a former prosecutor who now runs a company called Trajectory Communications, said she "went into prosecutor shutdown mode."
But later, after contacting her husband and the principal at her children's school, her hands were shaking and she felt nauseated. "I was scared," she said.
After she publicly said she refused to be intimidated, Volkman received an outpouring of support from military members.
"A brave military wife like you deserves respect not threats from coward ISIS sympathizers," one message said. Another said, "It was meant to cause fear but ended up creating solidarity and resolve."
Volkman says military families have been on high alert in the last six months following the rise of Islamic State in Syria and Iraq. She said the military community is aware of the threat posed by the group, but has not succumbed to fear.
"The most amazing thing that has come of these messages is that they've empowered the whole military community in solidarity rather than inspiring fear," she said. "It's raised the vigilance level, but has taken the terror out of it."
Even so, she said, the messages have elevated her security concerns:
"My head will be swiveling for a long time."