Sports broadcasting is big business, with the total value of media rights across the world passing the $60bn (£44bn) mark last year.
The increasing cost of rights deals results in higher prices for fans at home, especially if they choose to pay for multiple services to watch their team play.
To get round this, some resort to illegal streams of big events.
Enders say there are often multiple streams of individual events - such as high profile football games - each of which can have tens of thousands of people watching them.
Bosses of big rights holders, Sky and DAZN, have previously warned piracy is causing a financial crisis in the broadcast industry.
There is a risk for users too.
The Enders report says fans watching football matches, for instance, via illegal streams are typically providing information such as credit card details and email addresses, leaving them vulnerable to malware and phishing scams.