The group responsible for publishing National Security Agency data over the summer released hundreds of new files on Monday, exposing domains and Internet protocol addresses that could reveal who the agency has targeted over the last several years.

"The Shadow Brokers is having special trick or treat for Amerikanskis tonight," the group taking credit for the leak wrote in a blog post on Medium.

The information contains more than 300 folders with files allegedly taken from the Equation Group, a group that has been linked to attacks on foreign governments and thought to be representative of the NSA's elite Tailored Access Operations unit.

The files reportedly include 306 domain names and 352 IP addresses based in countries including Russia, China, and India, meaning the NSA used hardware based in those countries to mask its operations. The information provides a roadmap for victims to trace cyberattacks back to the agency.

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The group first published information from the Equation Group in August, and said it was seeking as much as $500 million to sell the rest of what it held. Experts quickly noted the data dated back to October 2013, making it largely obsolete, and speculated the Russian government was simply using the group as a front to embarrass the American intelligence community.

The FBI arrested 51-year-old NSA contractor Hal Martin at the end of that month for taking classified intelligence home from the agency, a discovery probably made as a result of the investigation into the Shadow Brokers. Martin was widely seen as a culprit in the leak, but subsequent reports undermined that theory, and the newest leak came as Martin remained in detention.

Writing in broken English, the Shadow Brokers maintained in their Monday message that they hoped to sell data they still possessed, and complained about a lack of media attention. "The Shadow Brokers is making special effort not to using foul language, bigotry, or making any funny. Be seeing if NBC, ABC, CBS, FOX is making stories about now?"

"Maybe political hacks is being more important? How bad do you want it to get? When you are ready to make the bleeding stop, payus, so we can move onto the next game. The game where you try to catch us cashing out!" they added.