I had a business trip in Washington, DC. One day, I was having dinner at a sushi bar and chatted with the guy sat by me. To my surprise that he works for homeland securtiy office. I asked him about name check and he said FBI does the name check. The length of the name check depends on the person's last name. According to him, FBI will check all applicants' last name in its database using computer programs. If the applicant has a common last name (such as Zhang) then there will be a long list. If there are some Zhangs have some problems in the US previously, this applicant might have better chance to get picked and duration varies case to case.