The U.S. National Security Agency has a cyberwarfare program that hunts for foreign cyberattacks and is able to strike back without human intervention, according to NSA leaker Edward Snowden.

The NSA cyberwarfare program, called MonsterMind, uses software to look for traffic patterns indicating possible foreign cyberattacks, according to Snowden, quoted in a lengthy profile in Wired.

MonsterMind could automatically block a cyberattack from entering the U.S., then retaliate against the attackers, according to the Wired story.

Snowden, when he was working as an NSA contractor, was concerned that MonsterMind could lead to misdirected counterattacks. “These attacks can be spoofed,” he told Wired. “You could have someone sitting in China, for example, making it appear that one of these attacks is originating in Russia. And then we end up shooting back at a Russian hospital. What happens next?”

MonsterMind also creates privacy problems, because it would have to access nearly all the communications coming into the U.S. in order to work, Snowden told Wired. “If we’re analyzing all traffic flows, that means we have to be intercepting all traffic flows,” he said. “That means violating the Fourth Amendment, seizing private communications without a warrant, without probable cause or even a suspicion of wrongdoing. For everyone, all the time.”

A program such as Snowden described would raise major concerns, the American Civil Liberties Union said.

“The government has used excessive secrecy to prevent real debate over the wisdom and legality of many of its most sweeping surveillance programs,” Alex Abdo, an ACLU staff attorney, said by email. “This newly described program is just another example of that secrecy. If the government truly is scanning all internet traffic coming into the United States for suspicious content, that would raise significant civil liberties questions.”

The NSA declined to comment on MonsterMind, but called on Snowden to return to the U.S. from Russia. “If Mr. Snowden wants to discuss his activities, that conversation should be held with the U.S. Department of Justice,” the NSA said in a statement. “He needs to return to the United States to face the charges against him.”

In addition to MonsterMind, the Wired story alleges that NSA hackers accidentally shut down Internet service in Syria for a short time in 2012 when trying to remotely install an exploit in one of the core routers at a major ISP in the country.

NSA workers were attempting to gain access to email and other Internet communications in Syria, but the router was destroyed in the process of trying to compromise it. The NSA was worried Syria would discover the exploit, but apparently didn’t, Snowden told Wired.