The National Security Agency revealed the identities of many more citizens, permanent residents and corporations who were mentioned in intelligence reports last year, in a process known as “unmasking” that has been a source of controversy for President Trump and his allies in Congress. 

But the statistics, released Tuesday in an annual report, may reflect an increase in the number of people or American businesses being victimized by a foreign government, including through computer hacks, and whose identities were revealed to warn them, a U.S. official said. 

In 2018, the NSA, which conducts legally authorized surveillance of communications overseas, unmasked the identities of 16,721 “U.S. persons,” a term that includes corporations, in response to a request from another government agency, according to the report from the Office of the Director of National Intelligence. That was a more than 7,000-person increase from 2017. 

In the course of monitoring communications abroad, the agency routinely picks up the communications of U.S. persons, whose identities are “masked” in reports that are circulated among government agencies, to protect their privacy. 

When the recipient of a report — for instance, an official at the CIA — can demonstrate a “need to know” that U.S. person’s identity, to assess the information in the report and its importance, officials and lawyers who review the matter can unmask it and show a name or other piece of identifying information. 

Trump and leading Republican members of Congress have alleged that Obama administration officials abused that process to leak the names of Trump transition officials who were in communication with foreign officials. Defenders of the process say that unmasking only occurs under strict legal review and is not designed to be punitive or to target Americans, but rather to protect U.S. interests.  

It wasn’t immediately clear how the administration or lawmakers would react to the sharp increase in unmaskings under the Trump administration. 

Alex Joel, who oversees civil liberties and transparency issues for the Director of National Intelligence, attributed the spike in part to foreign intelligence services that are trying to monitor U.S. individuals and companies. Foreign computer hackers have aggressively stepped up their efforts in recent years to steal private communications or pilfer trade secrets from U.S. companies.  

In recent years, the FBI has made an effort to warn Americans when a foreign government is trying to spy on U.S. persons or steal their communications, according to U.S. officials involved in the practice who spoke on the condition of anonymity to discuss the process.

Law enforcement officials often find out who is being targeted based on information collected overseas, including by the NSA. 

The new report emphasized that a single report from the agency could contain “multiple U.S. person identities, masked and/or openly named. For example, a single report could include a large number of U.S. identities that a foreign intelligence target is seeking to victimize; each of those identifiers would be counted.” 

The term “identity” also encompasses an email address or an Internet protocol address, the unique number that identifies a particular computer. So, the larger number of unmasked identities could consist of that information, in addition to names.

The report also took stock of a range of other authorized surveillance activities that the intelligence community conducts under the Foreign Intelligence Surveillance Act, but it didn’t disclose many dramatic changes. 

The total number of orders issued by the surveillance court in 2018, for instance, was around 1,100, a drop of about 250 orders from the previous year. But the estimated number of “targets” of those orders, which could be a person’s communications or a physical place, went up by about 37 percent, to just over 1,800. 

About 12.7 percent of those targets are estimated to be U.S. persons, according to the report. The figure includes surveillance that is conducted overseas and within the United States. 

It can be difficult to discern the reason that figures fluctuate form year to year, Joel said. 

The report notes that changes in world events, the priorities of a particular agency, new technical capabilities and changes in behavior by those who are being surveilled are all contributing factors. 

“These reasons often cannot be explored in detail in an unclassified setting without divulging information necessary to protect national security,” the report says. “Moreover, there may be no relationship between a decrease in the use of one authority and an increase in another.” 

Overall, Joel said that the report shows that the government is conducting surveillance in ways that “can be expected” given what the law allows. In cases where the numbers changed, it wasn’t because those legal authorities had changed, he said.