https://www.dni.gov/index.php/ic-legal-reference-book/foreign-intelligence-surveillance-act-of-1978
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Sec. 105
FOREIGN INTELLIGENCE SURVEILLANCE ACT OF 1978
(5) Paragraphs (5) and (6) of subsection (e) shall apply to this
subsection.
(g) Notwithstanding any other provision of this title, officers,
employees, or agents of the United States are authorized in the
normal course of their official duties to conduct electronic surveil-
lance not targeted against the communications of any particular
person or persons, under procedures approved by the Attorney Gen-
eral, solely to—
(1) test the capability of electronic equipment, if—
(A) it is not reasonable to obtain the consent of the
persons incidentally subjected to the surveillance;
(B) the test is limited in extent and duration to that
necessary to determine to capability of the equipment;
(C) the contents of any communication acquired are
retained and used only for the purpose of determining the
capability of the equipment, are disclosed only to test per-
sonnel, and are destroyed before or immediately upon com-
pletion of the test; and
(D)
Provided,
That the test may exceed ninety days
only with the prior approval of the Attorney General;
(2) determine the existence and capability of electronic sur-
veillance equipment being used by persons not authorized to
conduct electronic surveillance, if—
(A) it is not reasonable to obtain the consent of per-
sons incidentally subjected to the surveillance;
(B) such electronic surveillance is limited in extent
and duration to that necessary to determine the existence
and capability of such equipment; and
(C) any information acquired by such surveillance is
used only to enforce chapter 119 of title 18, United States
Code, or section 705 of the Communications Act of 1934,
or to protect information from unauthorized surveillance;
or