Tashfeen Malik, who along with her husband carried out a massacre in San Bernardino, Calif., passed three background checks by American immigration officials as she moved to the United States from Pakistan.
No one uncovered what Ms. Malik had made little effort to hide: that she talked openly on social media about her views on violent jihad. She said she supported it. And she said she wanted to be a part of it, the New York Times reported on Sunday.
American law enforcement officials said they recently discovered those old and previously unreported postings as they pieced together the lives of Ms. Malik and her husband, Syed Rizwan Farook, trying to understand how they pulled off one the deadliest terrorist attacks on American soil since September 11, 2001.
Had the authorities found the posts years ago, they might have kept her out of the country. But immigration officials do not routinely review social media as part of their background checks, and there is a debate inside the Department of Homeland Security over whether it is even appropriate to do so.
The discovery of the old social media posts have exposed a significant and perhaps inevitable shortcoming in how foreigners are screened when they enter the United States, particularly as people everywhere disclose more about themselves online.
Ms. Malik faced three extensive national security and criminal background screenings. First, Homeland Security officials checked her name against American law enforcement and national security databases. Then her visa application went to the State Department, which checked her fingerprints against other databases. Finally, after coming to the United States and formally marrying Mr. Farook here, she applied for her green card and received another round of criminal and security checks.
Ms. Malik also had two in-person interviews, federal officials said, the first by a consular officer in Pakistan, and the second by an immigration officer in the United States when she applied for her green card.
All those reviews came back clear, and the F.B.I. has said it had no incriminating information about Ms. Malik or Mr. Farook in its databases.
As part of their investigation into the electronic trail of Ms. Malik and Mr. Farook, investigators are searching for devices, including a computer hard drive that appeared to be missing from their home, and cell phones they might have abandoned.
Investigators are particularly interested in Ms. Malik’s life in Pakistan in the years before she moved to the United States. They believe that was when she was radicalised.
From 2007 to 2012, she lived in a university hostel and then with her mother and sister Fehda at a family home in Multan, Pakistan. In a brief telephone interview on Saturday, the sister, Fehda Malik, said Tashfeen Malik was not an extremist, and she rejected the allegations against her sister.
“I am the one who spent most of the time with my sister,” she said. “No one knows her more than me. She had no contact with any militant organisation or person, male or female.”
She said her sister was religious, studied the Quran and prayed five times a day. “She knew what was right and what was wrong,” Fehda Malik said. She added that the family was “very worried and tense,” before hanging up the phone.
