Britain's anti-doping authority has reassured athletes that no personal data was stolen as a result of a hacking attack on the authority over the weekend.
The U.K. Anti-Doping Agency did not identify the source of the hacking attempt in a statement disclosing the hack on March 26.
But the Russia-linked Fancy Bear hacking group has previously broken into sports bodies' files, including those of the World Anti-Doping Agency and International Association of Athletics Federations, and obtained private athlete information.
As a result of a previous hacking by Fancy Bear, the use of a banned drug by British cycling great Bradley Wiggins under therapeutic-use exemptions came to light last year.
Such exemptions, which are granted by the World Anti-Doping Agency in consultation with doctors, allow athletes to use otherwise banned drugs for medical reasons.
The five-time Olympic champion was administered the corticosteroid triamcinolone before his three biggest road races in 2011, 2012, and 2013, including his 2012 Tour de France victory.
Russian President Vladimir Putin recently criticized therapeutic-use exemptions and instructed Russian diplomats to try to change the international rules governing doping.
Hundreds of Russian athletes have been banned from global sporting events since 2015 as a result of anti-doping agencies' investigations into their alleged doping abuses.
"Over the weekend, U.K. Anti-Doping was made aware of a cyberattack affecting our systems. We can confirm that no data has been lost or compromised," the British agency said in a statement.
"We took the necessary steps to investigate and resolve the situation. No core activity, including our testing program, has been impacted," it said.
"We are satisfied that we have appropriate levels of cybersecurity in place, and we continually review our systems and measures to ensure they are of a very high standard."