A Marine pauses on Sept. 11, 2016, at one of the pools at the National September 11 Memorial after a morning commemoration ceremony for the victims of the 2001 terrorist attacks. (Spencer Platt/Getty Images)

Rachel Brand is associate attorney general.

As the recent event in New York and other attacks around the globe have shown, we face a constant threat from terrorists. The dedicated men and women in our intelligence community and law enforcement work tirelessly to identify and prevent such attacks.

But their ability to protect Americans is at risk. One of our most effective foreign intelligence tools — Section 702 of the Foreign Intelligence Surveillance Act — is set to expire at the end of the year if Congress does not act.

Initially enacted in 2008 and reauthorized in 2012, both times with broad bipartisan support, Section 702 is a critical national security tool with undisputed value. It has prevented multiple terrorist attacks, including an al-Qaeda plot to detonate explosives in the New York subway. Similarly, communications collected under Section 702 exposed the plans of an Islamic State network to attack members of our military abroad. Based on these and other examples, many of whose details remain classified, the nonpartisan Privacy and Civil Liberties Oversight Board, on which I served, unanimously found that Section 702 has been valuable and effective in protecting the nation's security.

Congress is working on legislation to reauthorize Section 702, but some of the proposed amendments, though well-intentioned efforts to protect Americans' privacy, would dramatically limit the ability of the intelligence community agencies — particularly the FBI — to uncover plots and prevent attacks. These amendments reflect fundamental misconceptions about how the provision works.

Most important, Section 702 does not allow the government to target Americans for surveillance, nor does it allow bulk collection of communications. Targets must be foreigners located outside the United States. And the government cannot target just any foreigner; there must be reason to believe that the foreigner's communications will reveal foreign intelligence information. If an American is emailing with a lawful foreign target, the government can collect only emails with that target — not any of the American's other emails.

Although the FBI receives data from only a tiny percentage (less than 5 percent) of Section 702 targets, and only when it relates to an ongoing national security investigation, bills pending in Congress would limit the FBI's ability to "query" this data during an investigation. A query is just a way of electronically looking through information the FBI already lawfully possesses in its databases; it does not collect any new information. It is a routine and minimally invasive tool that investigators use, particularly in the early stages of an investigation in response to a tip or a lead, to determine what the government already knows about a person before going out to collect other information.

For example, if someone phoned in a tip about a person who rented a truck under suspicious circumstances, the FBI would quickly query its databases to determine what information it already has about the person — including Section 702 information, which could reveal whether the person was in contact with foreign terrorists.

Many of the proposed amendments, which would make it more difficult for one FBI agent to know what other FBI agents or other intelligence agencies know, hark back to the "wall" that prevented information-sharing before 9/11. The 9/11 Commission's report explained how this wall — another well-intentioned effort to protect privacy — kept different parts of the government from sharing information about two of the individuals who eventually became the hijackers. After the 2009 Fort Hood shooting, an independent review commission again found that well-intentioned failures to share information kept the government from preventing the attack.

We cannot afford to make the same mistake again. To keep us safe, our intelligence agencies must be able to "connect the dots" between the various pieces of information the government already lawfully possesses. In reauthorizing Section 702, Congress must not forget the lessons we learned from 9/11.