I have been working at US Department of Homeland Security full-time (More than 8 years)
For those interested in how the screening and vetting of individuals seeking to enter the US legally functions and how it often provides unique insight into terrorist activity, DHS is great place to start.
The organization is still growing and finding its legs among more senior and well established members of the Intelligence Community
I applied through an employee referral. The process took 4+ weeks. I interviewed at US Department of Homeland Security (Jacksonville, FL).
Email correspondence, followed by phone interview (3). It was very simple, or at least more so than expected. Fairly straight forward with most questions referencing resume and future goals. The do ask about drug usage, illegal activity, legal trouble, etc. You do not have to receive any clearance, but they do background checks to make sure you are up to par.