Russian-linked ransomware gang websites blamed for attacks on hundreds of businesses worldwide have simply vanished from the internet.
Monitors say a payment website and a blog run by the REvil group became suddenly unreachable on Tuesday.
The reason behind the disappearance is unknown, but has sparked speculation that the group may have been targeted deliberately by authorities in Moscow after growing pressure from the US, the BBC is reporting.
US President Joe Biden said he raised the issue of cybercrime and ransom attacks with Russian President Vlamidir Putin during a phone call on Friday, after discussing the subject during a summit with him in Geneva last month.
Biden told reporters that he had made it very clear to Putin that the US expected him to act and also hinted the US could take direct digital retaliation on servers used for intrusions.
The timing of Tuesday’s outage has sparked speculation that either the US or Russian authorities may have taken action against REvil.
Officials have so far declined to comment and cyber experts say sudden disappearances of such groups are not uncommon.
The development comes after a series of high-profile ransomware attacks which have hit major US businesses this year.
The FBI accused REvil – also known as Sodinokibi – of being behind a ransomware attack on JBS, the world’s largest meat processing company, last month.
The group is considered prolific and last week demanded a huge bitcoin ransom for an attack which targeted IT firm Kaseya and hundreds more businesses worldwide.
One unidentified hacker who claims to be an affiliate of the gang talked to the BBC and claimed that the US “Feds took down” elements of their websites and so the gang pulled the plug on the rest of their operation.
He also said there was pressure from the Kremlin too, saying: “Russia is tired of the US and other countries crying to them.”
The BBC comments that if this scenario proves to be accurate, it shows a dramatic shift in policy from the Kremlin which has so far been happy to sit back and let gangs like REvil operate without fear of intervention and collect their enormous ransoms.