Reports have emerged of Yahoo’s (NASDAQ:YHOO) use of custom-built software to scan its users’ emails on behalf of federal investigators. Yahoo reportedly built a specialized program to search the incoming emails of its hundreds of millions of customers for the U.S. government. The Yahoo program as described in the report would be the first case of a U.S.-based Internet company searching all incoming messages.

According to reports, Yahoo was served with a classified U.S. government directive by either the National Security Agency or FBI and subsequently agreed to scan its users’ email. According to the company’s own previous admissions, either agency could have evoked FISA to obtain content created, communicated or stored with Yahoo’s services.

Yahoo released a statement saying, “Yahoo is a law-abiding company, and complies with the laws of the United States.” In another statement, the company said, “We narrowly interpret every government request for user data to minimize disclosure. The mail scanning described in the article does not exist on our systems.” A statement from the Office of the Director of National Intelligence suggests that the Yahoo email surveillance did not involve bulk collection of data.

Concerns have once again emerged over how the government goes about using its surveillance authority. There are questions about possible constitutional violations related to the use of the software. Some are saying that the Yahoo scandal epitomizes the need to reform the Foreign Intelligence Surveillance Court, the panel that authorizes spy orders.

The government may be altering the interpretation of a provision of the Foreign Intelligence Surveillance Act (FISA), Section 702, to get away with mass spying through tech companies. Under Section 702, U.S. investigators can collect the international communications of American citizens while conducting a terrorism or other high-stakes crime probe.

ODNI Public Affairs Deputy Director Richard Kolko said in the statement, “Under FISA, activity is narrowly focused on specific foreign intelligence targets and does not involve bulk collection or use generic key words or phrases. The United States only uses signals intelligence for national security purposes, and not for the purpose of indiscriminately reviewing the emails or phone calls of ordinary people.”

Rep. Ted Lieu, California Democrat who sits on the House Oversight and Government Reform’s Subcommittee on Information Technology, said in a statement, “If true, the government’s directive to Yahoo to write a software program and search all of its customers’ incoming emails for certain content is a gross abuse of Federal power. Private sector companies and private citizens are not an arm of law enforcement or an extension of our intelligence agencies.”

This is the second time in as many weeks that the company found itself in critics’ crosshairs. Late last month, Yahoo revealed a massive data breach that took place in 2014. The data breach exposed the account information of hundreds of millions of Yahoo’s customers. Verizon recently agreed to pay $4.8 billion to acquire Yahoo, but these incidents could threaten that acquisition.

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