Microsoft has revealed it is the latest high-profile company to have its computer system hacked.
In the last two weeks social media site Facebook and technology giant Apple have also admitted to being victims of cyberattacks.
Microsoft said it has experienced "a similar security intrusion" in a blog posted on its website on Friday.
Like the other recent victims, it added that there was no evidence of customer data being taken.
Spokesman Matt Thomlinson said the company waited until its initial investigation was over to reveal the attack.
He said: "During our investigation, we found a small number of computers, including some in our Mac business unit, that were infected by malicious software using techniques similar to those documented by other organisations.
"We have no evidence of customer data being affected and our investigation is ongoing."
Like Facebook, Microsoft says it is still investigating how malicious software was planted on what it said were a small number of its computers.
Online messaging service Twitter also recently revealed that hackers may have stolen information about 250,000 of its users.
Mr Thomlinson added: "This type of cyberattack is no surprise to Microsoft and other companies that must grapple with determined and persistent adversaries."