Here we go again. The Wall Street Journal reports that Russian hackers stole details of “how the National Security Agency penetrates foreign computer networks, the computer code it uses for such spying, and how it defends networks inside the U.S.” from the home computer of an NSA contractor in 2015.

Perhaps the most tantalizing (or troubling) detail from the report is that the newspaper claims the files were found using an exploit in a Kaspersky Lab antivirus program on the contractor’s computer—Russian software that the Department of Homeland Security recently banned for U.S. government use over security concerns. A spokesperson tells the Journal that the NSA doesn’t use Kaspersky antivirus software. Clearly, though, such protections don’t extend to the homes of contractors.

Perhaps the bigger point here is that yet another contractor has been able to remove files from the NSA’s network and get them into the outside world. (The most famous previous offender being Edward Snowden, though more recently Harold Martin also managed a similar feat.) And when a high-profile government agency keeps hemorrhaging sensitive data, that’s deeply worrying.

Or as Slate puts it rather more bluntly: “The U.S. can’t trust its own spy agency.”

As for the Kaspersky link, there are a couple of points worth bearing in mind. First, as Ars Technica points out, the newspaper provides no supporting evidence that the hack was achieved via Kaspersky software. And second, even if it was, it may have been an honest security flaw in the program rather than a deliberate back door built by the Russian state.

But that’s being generous. Now it will prove fascinating to find out if the suspicions of the DHS were founded all along.