(Reuters) – The U.S. government on Tuesday released an alert with technical details about a series of cyber attacks it blamed on the North Korean government that stretch back to at least 2009.

The warning is the latest from the Department of Homeland Security and the Federal Bureau of Investigation about hacks that the United States charges were launched by the North Korean government.

A representative with Pyongyang’s mission to the United Nations declined comment. North Korea has routinely denied involvement in cyber attacks against other countries.

The report was published as U.S. and North Korean negotiators work to resuscitate plans for a possible June 12 summit between leaders of the two nations. The FBI and DHS released a similar report in June 2017, when relations were tense between Washington and Pyongyang due to North Korea’s missile tests.

The U.S. government uses the nickname “Hidden Cobra” to describe cyber operations by the North Korean government, which it says target the media, aerospace and financial sectors and critical infrastructure in the United States and around the globe.

Tuesday’s report did not identify specific victims, though it cited a February 2016 report from several security firms that blamed the same group for a 2014 cyber attack on Sony Pictures Entertainment.

The alert provided a list of 87 IP addresses, four malicious files and two email addresses it said were associated with “Hidden Cobra.”

Last year’s alert was published on the same day that North Korea released American university student Otto Warmbier, who died days after his return to the United States following 17 months of captivity by Pyongyang

(Reporting by Jim Finkle in Toronto; Additional reporting by Rodrigo Campos in New York; Editing by Leslie Adler)