Updated Detectives have arrested two men in the UK this morning in connection with an international "conspiracy" to break into the Microsoft network.
The two 20-somethings are in police custody.
The coppers, based in the South East Regional Organised Crime Unit, are investigating "unauthorised intrusion into networks that Microsoft owns" between January and March 2017.
One of the suspects, a 22-year-old from Lincolnshire, was arrested on suspicion of gaining unauthorised access to a computer. The other, a 25-year-old from Bracknell, was arrested under Computer Misuse Act offences.
The detectives said they seized "a number of devices" during a raid today. The department did not clarify what information had been accessed by any alleged attacker. Microsoft confirmed to The Register that no customer information has been compromised.
"This group is spread around the world and therefore the investigation is being coordinated with our various partners," Det Sgt Rob Bryant said in a statement. SEROCU is collaborating with partners including Microsoft, the FBI, EUROPOL and the NCA's National Cyber Crime Unit.
Microsoft said: "Today's action by authorities in the UK represents an important step... Stronger internet security depends on the ability to identify and prosecute cybercriminals. This requires not only a strong technical capability, but the willingness to acknowledge issues publicly and refer them to law enforcement.
"No company is immune from cybercrime. No customer data was accessed, and we're confident in the integrity of our software and systems. We have comprehensive measures in place to prevent, detect, and respond to attacks." ®
Updated to add on June 27
The two chaps have been quizzed by cops and let go for now. "They were released pending further investigation. No one has been charged," a spokesperson for the South East Regional Organised Crime Unit told The Register.