An unnamed U.S. law firm was caught up in the global surveillance of the National Security Agency (NSA) and its overseas partners in Australia, according to a story in the New York Times.

A top secret document obtained by former NSA contractor Edward Snowden shows the firm was monitored while representing a foreign government in trade disputes with the United States, according to the paper.

The government of Indonesia retained the law firm for trade talks, which were under surveillance by the Australian Signals Directorate, said the report, citing the February 2013 document.

The Australian agency notified the NSA that it was conducting surveillance of the talks, including communications between Indonesian officials and the U.S. law firm and offered to share the information, according to the Times.

The Australians said that "information covered by attorney-client privilege may be included" in the intelligence gathering, according to the document, which the Times described as a monthly bulletin from an NSA liaison office in Canberra, Australia.

The law firm was not identified in the document, but Mayer Brown, a Chicago-based firm with a global practice, was then advising the Indonesian government on trade, the Times said.

A Mayer Brown spokesman did not respond to a request for comment.

The Times report quoted Mayer Brown lawyer Duane Layton, who was involved in the trade talks, as saying that he did not have any evidence that he or his firm had been under scrutiny by Australian or U.S. intelligence agencies.

"I always wonder if someone is listening, because you would have to be an idiot not to wonder in this day and age," he told the Times. "But I've never really thought I was being spied on."

Commenting on the report, Kent Zimmermann, a consultant at law firm consulting firm Zeughauser Group, told Reuters:

"It was only a matter of time before this happened to a U.S. law firm and was publicly reported ... There is a widely held perception that U.S. law firms are the soft underbelly of corporate America when it comes to vulnerability of spying and hacking."