For the second time since Russia’s offensive against Ukraine began, NSA leaker Edward Snowden has taken aim at the United States from Russian soil. The first occurred when he addressed SXSW via web video from an undisclosed location within Russia, where he has been granted asylum. That chat signaled to the world that President Obama and the United States are impotent to stop Snowden, and strongly suggested that Putin is controlling him. The latest disclosure, reported by the Washington Post, is about to cause a massive diplomatic headache for the United States.

The National Security Agency has built a surveillance system capable of recording “100 percent” of a foreign country’s telephone calls, enabling the agency to rewind and review conversations as long as a month after they take place, according to people with direct knowledge of the effort and documents supplied by former contractor Edward Snowden.

A senior manager for the program compares it to a time machine — one that can replay the voices from any call without requiring that a person be identified in advance for surveillance.

The voice interception program, called MYSTIC, began in 2009. Its RETRO tool, short for “retrospective retrieval,” and related projects reached full capacity against the first target nation in 2011. Planning documents two years later anticipated similar operations elsewhere.

In the initial deployment, collection systems are recording “every single” conversation nationwide, storing billions of them in a 30-day rolling buffer that clears the oldest calls as new ones arrive, according to a classified summary.

The call buffer opens a door “into the past,” the summary says, enabling users to “retrieve audio of interest that was not tasked at the time of the original call.” Analysts listen to only a fraction of 1 percent of the calls, but the absolute numbers are high. Each month, they send millions of voice clippings, or “cuts,” for processing and long-term storage.

At the request of U.S. officials, The Washington Post is withholding details that could be used to identify the country where the system is being employed or other countries where its use was envisioned.

The most likely targets are North Korea and Iran. Both are dangerous enemies bent on developing nuclear arsenals, and both are determined to cause havoc and destroy U.S. allies if not the U.S. itself. However, both North Korea and Iran are capable of surprising us with nuclear tests, missile launches and the like, so they may not be the targets, at least not yet. NSA might have developed the technology by targeting a much smaller and less governed country, say Yemen, with an eye to replicating it on a larger scale once the technology was sufficient. The U.S. does seem to find high numbers of terrorists to drone in Yemen.