While the movie has not been officially released for home audiences, versions filmed off cell-phones exist, being traded and downloaded on websites whose downfall has been long sought after by studios and Hollywood. Recently, it was discovered that one of the more popular downloads includes, hidden within the files, malware which turns your system into a crypto-mining tool.
What is crypto-mining? In a basic sense, it's the process which creates additional units of digital currency. To do this, a processor (or in a lot of cases these days, video/graphics cards) will run through complex puzzles, which once complete awards the user a specified value.
This means that those who pirated the new Spider-Man movie may have had their computers hijacked by threat actors, using up power to make someone else money. In this case, it's the cryptocurrency Monero.
Of course, there are other ways your computer may be hijacked without you knowing. It could come from any download or e-mail attachment. In most cases, crypto-mining uses a ton of energy. According to researchers at the University of California Berkeley, Bitcoin mining uses up .5% of the entire world's energy.
If your system has been compromised, you could be footing part of that bill. In this case, the best way to defend your system and electric bill is to simply, not pirate movies.