The company said in a blog post on Friday afternoon that it suffered the same security breach that Facebook and Apple have recently been dealing with.
Malware-infected websites contaminated some of Microsoft's computers, it said, adding that no customer data was compromised. Microsoft did not say when they discovered the breach.
"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 organizations," Matt Thomlinson, the general manager of Microsoft's security unit, said in the post.
The tech giant said it refrained from making a public statement during its initial investigation.
Also read: Twitter, Tumblr, Pinterest Hacked; Email Addresses Compromised
"This type of cyber attack is no surprise to Microsoft and other companies that must grapple with determined and persistent adversaries," Thomlinson said, adding that the company will "re-evaluate" its security strategy.
Earlier this month Twitter said 250,000 accounts were compromised when its system was breached. Then, Facebook said last Friday that it was the victim of a "sophisticated attack."
A New York Times report in January detailing apparent Chinese hackers infiltrating its internal systems prompted a sudden uptick in hacking, or at least in companies admitting to being hacked.
NBC.com was hacked in a malware attack on Thursday, potentially infecting any viewers that clicked over to the network's site.
On Tuesday, Apple said its systems were hacked, but no user data was compromised.
And earlier on Friday, a cyber attack on the customer support service Zendesk left Twitter, Tumblr and Pinterest scrambling to alert users whose email addresses were stolen.
