Microsoft has joined Facebook and Apple on the list of US technology giants targeted in recent cyberattacks.
In a blog posting on Friday, Microsoft said it had found no evidence that any customer data had been stolen.
The company gave few other details about the break-in, except to say that was it similar to a hacking attack that online social networking leader Facebook disclosed last week.
"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," Matt Thomlinson, Microsoft spokesperson, said in the blog post.
Facebook said it was "targeted in a sophisticated attack" last month, but that no user data was compromised.
The leading social network site said malicious software, or malware, that infected some of its machines came from a mobile developer website that had been booby-trapped.
Earlier this month, micro-blogging site, Twitter, disclosed that hackers may have stolen information about 250,000 of its users.
'Hunting down hackers'
Apple, the maker of iPhones, iPads, iPods and Macintosh computers, said on Tuesday that hackers invaded its system in an attack similar to the Facebook breach, but that it repelled the intruders before its data was plundered.
The California-based company said it was working with law enforcement officials to hunt down the hackers.
"The malware was employed in an attack against Apple and other companies, and was spread through a website for software developers," Apple told the AFP news agency.
The malware took advantage of a vulnerability in a Java program used as a "plug-in" for Web-browsing programs.
"There is no evidence that any data left Apple," the Silicon Valley-based company said.
While those behind the attacks have yet to be identified, computer security industry specialists have expressed suspicions about China-sponsored hackers and Eastern European crime gangs.