At least one virtual currency exchange was successfully compromised in late May.
According to the joint Russian-Chinese de-escalation plan, North Korea would stop work on its missile program in exchange for the US and South Korea halting large-scale war games, allowing tensions to gradually subside.
The heated words come as North Korea has been hit with tough sanctions. Other security firms have linked the group to past high-profile cyberattacks, including the hacking of Sony Pictures in 2014.
South Korea's won also edged down around the same time over domestic financial concerns. Kim Jong Un is very isolated. Or is it the people who suffer the most?
Aside from North Korea, reaction in Asia to the latest round of worldwide sanctions has been positive, but many are still skeptical they will have any significant impact.
"On this scale of threats, intimidation and insults it's probably just par for the course from North Korea", Foreign Minister Julie Bishop said on Wednesday.
Specifically, the hackers began targeting South Korean cryptocurrency exchanges. In early September, petrol cost an average of US$1.73 per kilogram, compared with 97 cents last December, according to data from the defector-run Daily NK. The new measures banned textile exports and capped fuel imports. FireEye identified the malware, known as PEACHPIT, and provided examples of documents it was attached to, including one published by Seoul-based Hyundai Research Institute about the state of bitcoin industries. FireEye didn't name the exchange.
"On the other hand, if North Korea continues its risky path, we will continue with further pressure", Haley concluded.
U.S. Ambassador to the U.N. Nikki Haley has called oil "the lifeblood of North Korea's effort to build and deliver a nuclear weapon". "They've been creative in how they use their cyber-espionage capability". The malware found in the emails were similar to variants linked to North Korean hackers suspected to the perpetrators of cyber-heists from global banks a year ago.
The resolution that passed reduces about 30 percent of oil imports to the country via an annual cap of two million barrels a year and bans the supply of natural gas to the country.
If hackers manage to compromise an exchange - as opposed to a single wallet - they can move cryptocurrencies around, then swap them for hard currencies like South Korean won or USA dollars, the FireEye researchers wrote.