In a last-ditch effort to sway Congress as they debate the overhaul of a foreign surveillance measure, the FBI has disclosed that it successfully used a controversial foreign surveillance tool to thwart a terrorist plot on U.S. soil last year. The bureau shared three newly declassified instances where it was able to protect national security by accessing data collected under the digital spying authority known as Section 702 of the Foreign Intelligence Surveillance Act (FISA).

One of these instances involved the prevention of a "potentially imminent terrorist attack" against critical infrastructure in the United States. The disclosure comes as the expiration date of the spying tool is approaching in April, with renewal depending on the decision of Congress.

The House is expected to vote as early as Thursday on a major change to the foreign surveillance authority. This change, which has bipartisan support, would require the FBI to obtain a warrant or court order before searching a database of emails, texts, and other digital communications for information on U.S. citizens. The FBI is actively campaigning to sway undecided lawmakers and those open to reconsidering the legislation.

A senior FBI official, speaking anonymously, emphasized the potential damage of implementing the warrant requirement. They argued that by accessing the Section 702 database without a court order, the FBI was able to identify a person located within the U.S. who was in regular contact with a foreign terrorist group. The individual had acquired means to carry out an attack and had specific targets in the U.S. The FBI successfully foiled the plot approximately 30 days after uncovering it.

In addition to thwarting the terrorist plot, the FBI's access to the Section 702 database was instrumental in uncovering a foreign adversary's attempt to acquire technology for biological weapons production. It also revealed that a subject of a national security investigation was communicating with multiple foreign intelligence suspects, identified by other bureau field offices. The FBI believes that using slower investigative tools, such as a warrant, may have compromised the discovery of these crucial connections.

The compromise bill to update and renew Section 702 will be considered, with lawmakers expected to vote on an amendment regarding the court order provision. The White House is strongly against the amendment, and opposition in the Democratic-led Senate is anticipated.

During the briefing on the looming vote, National Security Adviser Jake Sullivan will emphasize the potential damage to national security if the court order amendment is approved. However, a bipartisan group of lawmakers argues that judicial oversight is necessary to prevent violations of Americans' privacy.

The FBI and the Biden administration have consistently contended that imposing additional restrictions could severely hinder one of the country's most valuable intelligence tools.

While the FBI's specific examples highlight the drawbacks of proposed reforms, privacy advocates continue to push for exceptions for national security matters within the court order mandate. In the case of the foiled terrorist attack, the FBI official argues that the initial searches were crucial in revealing the imminent threat.

As Congress debates the future of Section 702, the decision will not only impact national security but also raise important questions about privacy and the balance between law enforcement and civil liberties.