the counter-terrorism efforts of the United States. (3) The number of counterintelligence, intellectual property theft, and counterproliferation cases involving nationals of the country. (4) Any other criteria the Secretary determines appropriate. (c) Collaboration To carry out the requirements of subsection (a), the Secretary may collaborate with the following: (1) The head of a national laboratory within the Department’s laboratory network with relevant expertise. (2) The head of a relevant university-based center within the Department’s centers of excellence network. (3) The heads of other appropriate Federal agencies. (d) Waiver The Secretary, in collaboration with the Secretary of State, is authorized to waive the requirements of subsection (a) as necessary to comply with international obligations of the United States. 447. Open source screening The Secretary shall, to the greatest extent practicable, and in a risk based manner, review open source information of visa applicants. . (b) Clerical amendment The table of contents in section 1(b) of the Homeland Security Act of 2002, is amended by inserting after the item relating to section 445, as added by this title, the following new items: Sec. 446. Social media screening. Sec. 447. Open source screening. . 423. Homeland security investigations national gang unit (a) In general Subtitle D of title IV of the Homeland Security Act of 2002 ( 6 U.S.C. 231 et seq.), as amended by this title, is further amended by adding at the end the following new section: 448. National Gang Unit (a) Establishment There is established within the Department a program, which shall be known as the Homeland Security Investigations National Gang Unit (referred to in this section as National Gang Unit . The National Gang Unit shall be headed by an Assistant Director, who shall be appointed by the Executive Associate Director of United States Immigration and Customs Enforcement, Homeland Security Investigations. (b) Purpose The purpose of the National Gang Unit shall be to— (1) lead