In no particular order, and those I find helpful and interesting. Some of these folks are friends and colleagues. Note that some accounts don't always tweet about national security - but when they do, they share interesting stories and perspectives. Enjoy.

@froomkin - Dan Froomkin now at the Intercept.
@attackerman - Spencer Ackerman, formerly a reporter at the Danger Room blog at Wired, now at The Guardian.
@rhodes44 - Ben Rhodes, White House Deputy National Security Advisor for Strategic Communications & Speechwriting.
@QWiktorowicz - Quintan Wiktorowicz, former White House official, entrepreneur
@hoffman_bruce - Bruce Hoffmann, director of the Security Studies Program at Georgetown University's School of Foreign Service
@StateDeptCT - U.S. Department of State Counterterrorism Bureau
@CNSFordhamLaw - The Center on National Security at Fordham Law School.
@JessicaEStern - Author of Denial, Terror in the Name of God, The Ultimate Terrorists & other articles on terrorism; policy consultant and lecturer on counterterrorism and PTSD.

I'll add more from time to time. Do you have others to suggest? Let me know in the comments below.