WASHINGTON -- The White House's acting cybersecurity czar announced her resignation Monday, in a setback to the Obama administration's efforts to better protect the computer networks critical to national security and the global economy.

The resignation highlights the difficulty the White House has had following through on its cybersecurity effort. President Barack Obama first outlined his cybersecurity plans in a high-profile speech May 29, announcing his intention to create a top White House cybersecurity post -- a position...