Security Advisory Opinion Fact Sheet (for download here)
The Security Advisory Opinion (SAO) is a process the State Department utilizes to decide to grant or deny US visas to certain applicants. Started following September 11, 2001, SAO checks are an additional security mechanism, typically used to detect for espionage, terrorism, or illegal transport of technology. SAOs have also been used for extra screening of refugees.
US Government Agencies involved in SAO
SAO processing is a multi-agency review managed by the Department of State. After the Department of State flags the need for an SAO, depending on the type of SAO, it is then forwarded to one of the following: the State Department’s Bureau of International Security and Nonproliferation, the Department of Homeland Security (DHS), the Federal Bureau of Investigation (FBI) National Name Check Program (NNCP), the Central Intelligence Agency (CIA), the Drug Enforcement Agency (DEA), the Department of Commerce, the Department of Treasury’s Office of Foreign Assets Control, and may involve working with Interpol.
What factors trigger an SAO?
All nationalities are potentially subject to the SAO review process. Prior to the new EO, all male refugees ages 16-50 from 11 countries (plus stateless individuals residing in one of the 11 countries) were already flagged for SAO processing.
With the new EO, no refugees from these 11 countries will be processed through SAO for a period of 90 days, ending January 22, 2018. There are 9 types of SAO visas. Visa Merlin applies to refugees and asylees. SAOs for refugees are valid for 15 months.  
For refugees, the SAO process begins at a Resettlement Support Center (RSC) when their applications are screened.   Any of the below circumstances can trigger the need for an SAO across all visa categories, including refugees:
● the applicant's name is flagged in CLASS;
● an applicant received an unfavorable SAO in the past;
● the applicant is a national of a country not recognized by the United States or with which the United States does not maintain diplomatic relations;
● the U.S. interviewing U.S. consular officer has knowledge or a reasonable ground to believe that the applicant is ineligible for admission to the United States because of national security concerns (for example, the consular officer believes that the applicant might be involved in the transfer of sensitive technology designated by the Department of State (DOS)’s Technology Alert List (TAL));
● the applicant is a national or employee of a State Sponsor of Terrorism.
SAO processing times
There is very limited information about how long SAOs take; according to the State Department, most administrative processing is resolved within 60 days of a visa application interview; however, each consulate has their own specified processing times and the FBI states that 97 percent of certain types of SAOs are completed within 120 days. For refugees, there is little to no information available as to how long SAO checks take.
 Egypt, Iran, Iraq, Libya, Mali, North Korea, Somalia, South Sudan, Sudan, Syria, and Yemen.