Once again, the U.S. government is grappling with a leak that threatens to expose important military secrets and to undermine the confidence of its allies.

An arrest has been made, but the incident again raises concern about the ability of the U.S. government to protect its secrets and those of its partners. It looks increasingly as though embarrassments like this are a cost of doing business for a sprawling national security establishment.

Last week, The New York Times revealed that dozens of classified military documents had appeared some time ago on Discord, a chat service popular with gamers. The servers are like online clubs — some open to the public, others by invitation only — in which members exchange information. Reportedly, the documents had been circulating for some time and had been moved from one server on Discord to another, and were then disseminated more widely across the internet.