Military officials have advised U.S. service members to keep a low profile on social media and in public after members of the Islamic State, or ISIS, posted the names of 100 American troops online from information they reportedly gathered via Facebook and Twitter. A memo from Peterson Air Force Base in Colorado Springs, Colorado, was sent to a long list of troops earlier this month and said the terrorist group was trying to use service members’ biographical data to attack or intimidate their families, the Washington Times reported Monday.

The military base has warned personnel against sharing private information about their families and children online, and to avoid putting stickers on their vehicles or decorations on their homes that could indicate their affiliation with the military. “These organizations are attempting to use our own personal information against us to create fear and anxiety among our ranks and within our families,” a statement from U.S. Northern Command read, according to the Times. “We all have a responsibility to protect ourselves and our fellow service members and their families. We must reduce our vulnerabilities through active and vigilant monitoring of the information provided via the Internet and social media sources.”

The memo also advised troops to “be on the lookout” for devices that could be tracking their movements and to disable them. Troops also were told to make an effort to blend into the community.

The U.S. has conducted hundreds of airstrikes against ISIS in both Syria and Iraq since the war with the terrorist group began last summer. The U.S. has spent $1.83 billion in countering ISIS, Business Insider reported.

In March, ISIS released online what it called a target list including the names and addresses of 100 U.S. military members. The statement called on people living in the U.S. who were sympathetic to the terrorist group’s cause to find and kill them, Pentagon officials indicated. The list appeared to contain the names of troops mentioned in news articles about U.S.-led airstrikes against the Islamic State, the New York Post reported.