International sport - specifically sport between nations - has often been described as war by other means.

The hack of WADA's database of athlete medical records, perpetrated by a group called Fancy Bear, is the latest round in an escalating battle over anti-doping and perceived fairness in sport.

WADA condemned the hack, saying it was "very conscious of the threat that it represents to athletes whose confidential information has been divulged through this criminal act".

So what were Fancy Bear's claims? The hackers were going after the US Olympic Team, and its success at the Rio Games.

"As predicted, the USA dominated the 2016 Olympics medal count with 46 gold, 37 silver, 38 bronze for 121 total (medals). The US team played well but not fair," they said on their website.

The evidence? On its website Fancy Bear published illegally-accessed medical records, purporting to show that high-profile athletes such as gymnastic superstar Simone Biles and tennis stars Venus and Serena Williams took substances on the banned list.

How do TUEs work? A TUE (Therapeutic Use Exemption) is an exemption that allows an athlete to use, for therapeutic purposes only, an otherwise prohibited substance or method

A TUE (Therapeutic Use Exemption) is an exemption that allows an athlete to use, for therapeutic purposes only, an otherwise prohibited substance or method The Australian Sports Drug Medical Advisory Committee (ASDMAC) is the body that provides approvals for TUEs.

The Australian Sports Drug Medical Advisory Committee (ASDMAC) is the body that provides approvals for TUEs. TUE approval may protect athletes from receiving a sanction if a prohibited substance is found in their sample

TUE approval may protect athletes from receiving a sanction if a prohibited substance is found in their sample Exemptions are only granted if there is no unfair advantage given to the athlete by taking the substance or using the method (Info: ASADA)

This was perfectly legal, however, because the athletes concerned had received a TUE - or Therapeutic Use Exemption.

This meant that they had official approval to use the relevant substance for a medical condition.

In the case of Biles, who hit the headlines in Rio winning four gold medals in artistic gymnastics including the women's all-around title, she had tested positive during the Games to "methylphenidate and its metabolite Ritalinic Acid".

The files, however, also showed she had medical approval dating back to 2012 - extended repeatedly up to December 2018 - for the drug Focalin, used as a stimulant to the central nervous system.

American Simone Biles was the star of gymnastics at the Rio Olympics, winning four gold medals. ( AP Photo: Dmitri Lovetsky )

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Biles went public, confirming that she had had ADHD for years, requiring medication.

The Williams sisters - who have each won an Olympic women's singles title and three doubles titles together as a pair, dating back to the Sydney Olympics - were also mentioned by Fancy Bear.

The documents indicated that both sisters had taken a number of restricted substances between 2010 and 2015. Individually, these included prednisone, prednisolone, methylprednisone, hydromorphone and oxycodone.

But both athletes had received TUEs for the medication from relevant sports governing bodies.

American Serena Williams failed to win a medal in Rio, but but she has four previous tennis gold medals at the Olympics. ( AP Photo: Charles Krupa )

The head of the US Anti-Doping Agency, USADA, Travis Tygart, put out a strongly-worded statement referring to hackers making an "attempt to smear athletes to make it look as if they had done something wrong.

"The athletes haven't. In fact, in each of the situations, the athlete has done everything right in adhering to the global rules for obtaining permission to use a needed medication," he said.

Not everyone is so sanguine about the way the system works, however.

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Irish journalist Ciaron Lennon was one person who tweeted his thoughts about what the use of TUEs might mean for sport.

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The former head of ASADA, Richard Ings, posted on Twitter that TUEs were nothing new and quite common in this country.

The fact that TUEs were a part of Australian sport might come as a surprise to people not intimately acquainted with the way the system works.

And the numbers of exemptions handed out could potentially be a matter of concern to some.

In any case, given that the use of these medications by Biles and the Williams sisters was legal and above board, why has Fancy Bear publicised the hack?

The Russian connection

Here we come back to the idea of war by other means.

The last 18 months has seen a string of revelations about doping in Russian sport, initially focusing on athletics but then spreading to a range of other sports.

The key allegations were made by Grigory Rodchenkov, the former head of the Moscow Anti-Doping Laboratory.

Rodchenkov claimed dozens of Russian athletes had used performance-enhancing drugs at the Sochi Winter Olympics in 2014, where Russia had topped the medal table with 13 gold and 33 total medals.

A report by Canadian sports lawyer Richard McLaren backed Rodchenkov's allegations, confirming extraordinary levels of systemic abuse, including the concealment of hundreds of positive drug tests in many sports ahead of Sochi.

This culminated this year in the decision by the International Olympic Committee to ban almost the entire Russian athletics team, weightlifting team and various other athletes from Rio, while stopping short of a blanket ban.

The International Paralympic Committee went further, issuing a blanket ban, from both the Rio Paralympics and the next Winter Games in Pyeongchang, South Korea in 2018.

The debate over doping, anti-doping controls and the move to collective punishment grew acrimonious and cast a shadow over the Rio Olympics and beyond.

The decisions made incensed the Russian government - President Vladimir Putin had previously warned of an Olympic split and a "dangerous relapse of politics' interference into sports," and he responded to the bans by saying the absence of top Russian competitors would markedly lower the quality of the Rio Games.

Fancy Bear has been linked with Russian interests, but it is hardly the only group raising concerns over the conduct of world sport as regards doping.

Fancy Bear says this week's first publication is just "the tip of the iceberg" and that "today's sport is truly contaminated while the world is unaware of a large number of American doping athletes".

It seems no coincidence that the first release relates to the US, which was vocal in calling for Russia to be banned from Rio.

WADA's response to the hack made clear who it thought was behind the move.

"WADA has been informed by law enforcement authorities that these attacks are originating out of Russia," WADA's director-general, Olivier Niggli said.

"Let it be known that these criminal acts are greatly compromising the effort by the global anti-doping community to re-establish trust in Russia further to the outcomes of the Agency's independent McLaren Investigation Report."

On the same day as the hack went public, the IOC announced sanctions for four athletes who had failed re-testing of stored samples taken at the Beijing and London Olympics in 2008 and 2012.

All four athletes were Russian, including javelin thrower Maria Abakumova, who won a silver medal at the Beijing Olympics.