The company has said that thousands of bots are no longer receiving commands and attributed it to earlier legal action.
With a restraining order in hand, Microsoft is working to take down the spambot, which has infected hundreds of thousands of PCs worldwide.
Researcher warns people to be cautious about clicking on links related to Independence Day videos in e-mails over the holiday.
The software giant is on the verge of getting a court to grant it ownership over domains used in the Waledac spam botnet.
Botnet was responsible for 18 billion spam messages a day -- about 18 percent of the world's spam -- experts tell The New York Times.
Provider of free domains has agreed to delete or to transfer to Microsoft all subdomains the software giant had said were tied to the Kelihos botnet.
Spam levels increase more than 5 percent in February over prior month, due in large part to greater activity from Grum and Rustock botnets, according to Symantec.
The pair, who are linked to a malware network that stole more than $100 million, are already in custody in the U.K.
A Czech resident is accused of operating a botnet that infected tens of thousands of computers, serving spam and harvesting data. This is the third botnet Microsoft has taken down using the same legal and technical measures.
Waledac botnet is "decimated," ad companies in China worry their businesses are in danger if Google pulls search operation, Bing Maps goes stargazing.