With the tensions running high between the US and North Korea, there was bound to be some poking and prodding.

According to The Daily Mail, North Korea may have committed an act of war against the US via sabotage. It is believed that hackers working with North Korea attempted to hack into US power companies.

FireEye, an Internet security firm, reported that a number of emails were sent to various electric companies as part of a phishing hack attempt. The emails were invites to a supposed fundraiser and required the reader to download the attachment to see the invitation. Anyone who would’ve downloaded the attachment would’ve released malware and other viruses into their computer, thereby granting access to the power company network.

Though no specifics were given about the size of the attack or how successful it was, FireEye believes the attempted hack was a result of the ongoing tension between the US and North Korea.

According to the Internet security firm, the hacks were nothing more than “early-stage reconnaissance,” perhaps to detect potential weaknesses or exploitable areas within the systems. They did not believe the hacks were part of an “imminent disruptive” attack.

FireEye stated that North Korea is no stranger to cyber attacks: “North Korea linked hackers are among the most prolific nation-state threats, targeting not only the US and South Korea but the global financial system and nations worldwide.”

They went on to say North Korea’s attitude about hacking other nations is similar to how they treat their own nuclear program, ignoring the consequences or sanctions. “Their motivations vary from economic enrichment to traditional espionage to sabotage, but all share the hallmark of an ascendant cyber power willing to violate international norms with little regard for potential blowback,” FireEye stated.

Former chief of counterintelligence at the FBI, C. Frank Figliuzzi, said North Korea’s cyber attacks are a growing threat. “This is a signal that North Korea is a player in the cyber-intrusion field and it is growing in its ability to hurt us.”

This probing of US electric companies comes shortly after announcements that North Korea allegedly stole classified military documents from South Korea. Among those documents was information on how to assassinate Kim Jong-un and the other leaders of the DPRK, such as known hiding locations, movements, and how to disrupt their security efforts, among other things.

This hack occurred September 2016 with at least 235 gigabytes of documents stolen from the Defense Integrated Data Center. It was confirmed that North Korea executed the attack, but it was not revealed what information was taken, although officials claim it was not top classified information that would’ve compromised the US or South Korean military. It was also revealed that not all of the operational plans would’ve been leaked because not all of them were contained on the network.

According to NBC News, the hack itself is not inherently an act of war but could be considered one if it poses a great enough threat to American life, commerce, infrastructure, or other key components of the nation. Considering the hack was a reconnaissance operation and not an attack, it posed little threat and might not be considered an act of war by President Trump.

It does reveal, however, the lengths North Korea may go to disrupt the American way of life and sow doubt and uncertainty. It proves that even if North Korea’s nuclear arsenal is removed, they could still resort to cyber warfare to attack their enemies and spread chaos.