Ghost followers

Ghost followers, also referred to as ghosts and ghost accounts or lurkers, are users on social media platforms who remain inactive or do not engage in activity. They register on platforms such as Twitter and Instagram. These users follow active members, but do not partake in liking, commenting, messaging, and posting. These accounts may be created by people or by social bots.
Ghost follower scams.
Many ghost followers are accounts created by scammers who create fictional profiles and use them to target and scam others.
Buying followers.
Commercial services provide the ability to buy Instagram followers, most of which are ghosts. These individuals are paid to follow accounts but are not required to engage with them. This allows those seeking publicity to quickly increase their number of followers and appear to be popular, or "trending". For example, Rantic (formerly "SocialVEVO" and "Swenzy") was able to increase the number of Daily Dot's Twitter followers from 48,000 followers to 122,000 in only four days. This faux-popularity may still attract "volunteer" users. However, this technique may backfire if its use becomes known. According to Olivier Blanchard, unless the objective is just to appear popular, purchased ghosts do not help meet business objectives, other than possibly a form of brand marketing.
In January 2018 an article in the "New York Times" described the business of a company called Devumi in selling ghost followers on Twitter, and named many of Devumi's customers.
Rantic.com.
Rantic is perhaps the most widely publicized seller of ghost followers. According to a New York Times report, Rantic's clientele includes corporations, celebrities, journalists, politicians and even governments. The company rose to international mainstream media attention over its "controversial" bots, which can reportedly generate millions of user accounts on social media platforms. 
These ghost followers are being purchased for many popular social platforms including Instagram, Facebook and Twitter, and SoundCloud.
As a result, the practice of selling ghost followers has turned into a multimillion-dollar online business, according to another New York Times report.
Removal.
As of 2014, removing a ghost requires accessing the account and explicitly blocking it. This will immediately remove the connection between the ghost follower and your account. Ghosts can be avoided by marking an account as private, requiring would-be followers to request permission.
Since May 2018, Twitter has been trying to clean up its platform from phony records who ruined the experience of the real social media users. Their objectives run from trolling, cyberbullying, and most importantly controlling political talk or even to con influencer advertisers into forking over cash to fake web-based social networking influencers.