That's not an insignificant number, and it's understandable why Spotify is cracking down on them. As the company explains in an amended F1 filing with the SEC this week, these users forced the company to adjust its metrics and key performance indicators. The disclosure notes, "Unauthorized access to our Service may cause us to misstate key performance indicators, which once discovered, corrected, and disclosed, could undermine investor confidence in the integrity of our key performance indicators and could cause our stock price to drop significantly."

As a result, Spotify has adjusted its monthly active users from 159 million at the end of 2017 to 157 million. Considering the company has filed for a direct listing to go public, these numbers matter more than ever. In an email at the beginning of March, Spotify notified users of hacked apps that they were at risk of having their accounts suspended or terminated if they didn't cease using them immediately. Now, these numbers tell us why the company is concerned.