A Premier League club came close to losing £1m during a transfer deal because of cyber hackers.
The National Cyber Security Centre (NCSC) said it was only the intervention of the unnamed club's bank that stopped the theft.
It was one of several incidents highlighted as evidence that sport needed to improve its cybersecurity.
"The impact of cybercriminals cashing in on this industry is very real," said the NCSC's Paul Chichester.
A new report from the NCSC says the email address of a Premier League club's managing director had been hacked during a transfer negotiation, leading to the attempt to steal the £1m.
The report also says that a Football League club was targeted by hackers who cut off its security systems, blocking turnstiles and almost resulting in a fixture postponement.
And it added that in one incident a member of staff at a racecourse lost £15,000 after attempting to buy groundskeeping equipment from a fake version of eBay.
Sir Hugh Robertson, chair of the British Olympic Association, said in the report: "This report is a crucial first step, helping sports organisations to better understand the threat and highlighting practical steps that organisation should take to improve cybersecurity practices."