(The Hill) – A trove of purported Pentagon documents have appeared online in recent days, revealing information ranging from U.S. assessments of the Russia-Ukraine war to intel on how America may be spying on adversaries and allies. 

The source of the leaks is not yet clear. Reuters reported that three unnamed U.S. officials said  Russia or pro-Russian elements are likely behind at least the first batch of leaks.

Here’s what we do know so far about the documents: 

Are the leaked documents authentic? 

It’s not yet clear whether all the material surfacing online is legitimate, though unnamed U.S. officials have told CNN and the New York Times that the documents appear to be real.

However, some have also noted that, even if the documents are authentic, some of the information in them may have been altered.

Estimates of Russian troop deaths in certain documents, for example, are significantly lower than those given by U.S. officials, sparking some concern that the material could have been tweaked to spread misinformation. 

Ukrainian officials on Sunday said the leaks were an “ordinary game” by Russia’s secret services.

“To take open briefings, add fake info or certain parts of interceptions & publish them on social networks legalizing the ‘leak,’” said Ukrainian presidential adviser Mykhailo Podolyak on Twitter.

What’s in the files?

A number of documents resemble daily, non-public updates from the U.S. military’s joint staff and appear to detail U.S. and NATO aid to Ukraine, including notes on the progress of weapons aid. The documents on Russia and Ukraine don’t appear to include details on the warfare or plans of an expected Ukrainian offensive. 

According to the New York Times, which first reported on the leaked documents, the materials also indicate the U.S. has been spying on not just Russian but also Ukrainian leaders in an effort to monitor the war’s dynamics. 

Additional documents include U.S. intelligence agencies’ analyses, based on classified sources, about Russia and several countries, according to the Washington Post. Some materials reportedly appear to show how the U.S. tracks Russian forces with satellite imagery and where the Central Intelligence Agency has recruited some agents. 

The New York Times also reports that other materials suggest the U.S. is spying on Israel and South Korea, and include national security details on the Middle East and China.

Israel on Sunday denied allegations in the documents that leaders of its Mossad intelligence service had encouraged agency staff and Israeli citizens to participate in last month’s protests against the government’s proposed judicial reforms.

Another document detailed internal discussions among South Korean officials about U.S. pressure for Seoul to change its policy of not supplying weapons to Ukraine, per Reuters.

What has the U.S. said?

Pentagon deputy press secretary Sabrina Singh said in a statement on Friday the Department of Defense “is actively reviewing the matter, and has made a formal referral to the Department of Justice for investigation.”

The Justice Department has since opened an investigation into the leaks, according to The Wall Street Journal and other outlets.

A U.S. official told the Associated Press that even if the documents are legitimate, the intelligence value to be gleaned is likely minimal, because Russia would already know or be able to find out much of what was included. But others have expressed concerns that the breach could have serious security implications.

U.S. officials are working to remove the materials from the social media platforms to which they were posted, according to Voice of America.

What have other countries said?

Adriy Yusov of the Ukrainian Defense Ministry’s intelligence directorate sought to downplay concerns raised in the documents about Ukrainian ammunition supplies and air defense capabilities, saying, “It is not a secret for anyone that Ukraine asks questions about aviation, tanks, ammunition and other things.”

However, Ukrainian President Volodymyr Zelenskyy has said he and his senior staff had a meeting about how to prevent leaks of the country’s defense plans.

A South Korean presidential official said South Korea planned to discuss the leak with Washington, according to the New York Times.

However, the official declined confirm any details from the leaked documents, per Reuters.

Israel has offered the strongest statement rebuking the contents of the leaked documents, responding to the claim that leaders of its spy agency helped foment anti-government protests.

“The report that was published overnight in the American press is mendacious and without any foundation whatsoever,” the Israeli prime minister’s office posted on behalf of the Mossad.

“The Mossad and its senior officials did not — and do not — encourage agency personnel to join the demonstrations against the government, political demonstrations or any political activity.”