Microsoft presented the updated figure during a discussion of private and public sector cooperation when battling cyber crime.
The company is expected to pay close to $2.7 billion once the deal is finalized later this year.
In a three-part test that looked at accuracy, protection and false positives, Microsoft's free antivirus program finished at the bottom.
Microsoft on Wednesday suggested that newer versions of Exchange and Exchange Online are now so secure that it's less necessary to check for unauthorized users.
Microsoft, who has denied being involved with Prism since the program was first divulged, released a statement this week saying it did not provide the NSA with a backdoor to access personal Outlook.com e-mails and Skype conversations.
Microsoft soon will begin moving customers off an older Exchange security service.
This month's Microsoft Security Update also comes with word of a new policy for vulnerable apps in the Windows Store.
In lab tests, Microsoft's latest browser blocks 99 percent of malware attacks. But can lab-tested attacks accurately represent real-world attacks?
Found a hole in Microsoft's latest version of Windows? You could be awarded $100,000.
Microsoft is just one of many who have been sharing information on hardware specs and software vulnerabilities with government organizations.
According to Websense, a San Diego-based information security solutions provider, most browser Java installations continue to be unpatched or outdated, leaving the majority of users vulnerable to exploit code already in use in the wild.
- By John K. Waters
The cumulative security bulletin for Microsoft's Web browser addresses 19 separate flaws.
This month's security update will bring Microsoft's bulletin total for the year up to 51.
New features include updates to Windows Defender and Internet Explorer.
McAfee was the big winner, as its revenue increased 37 percent year-over-year.
To provide real-time information on newly discovered threats, Microsoft this week launched its Cyber Threat Intelligence Program (C-TIP), a program that will alert ISPs and emergency response teams of newly infected systems.
Microsoft this week published an assessment of organizational IT security, based on its own survey tool.
Organizations in over 100 countries has been in the cross hairs of this cyber ring that originates in China.
The infamous Trojan that's rolled up into widely used exploit kits is getting a new trick.
The malicious plugin could allow attackers to post on your behalf on the social networking site.