The blog post came after Microsoft criticized Google for misleading customers about its compliance with the standard.
At issue is whether Google Apps has achieved certification under the Federal Information Security Management Act. FISMA set a stringent security standard that some federal agencies must require their vendors to comply with.
On Tuesday, Microsoft pointed out recently unsealed U.S. Department of Justice court documents that say Google Apps for Government does not have FISMA certification, even though the company's websites say it does.
"Let's look at the facts," Eran Feigenbaum, director of security for Google Enterprise, wrote on Wednesday. He said Google Apps received FISMA certification from the General Services Administration in July 2010. Google has since started using the name "Google Apps for Government" to describe the service and has added two "security enhancements," he wrote.
"In consulting with GSA last year, it was determined that the name change and enhancements could be incorporated into our existing FISMA certification. In other words, Google Apps for Government would not require a separate application," Feigenbaum wrote.
However, while the service didn't require a new application, it apparently did require re-certification. In testimony in front of the U.S. Congress on Tuesday regarding the issue, Dave McClure from the GSA said that when products change, vendors have to recertify them, according to a Business Insider report. He confirmed that the agency is going through a recertification process for Google Apps for Government, which he called a "subset" of the original service, Google Apps Premier, that was initially certified.
The disagreement, then, appears to be over whether Google should say Google Apps for Government is FISMA certified while it is going through the recertification process. The company firmly argued it should.
"FISMA anticipates that systems will change over time and provides for regular reauthorization--or re-certification--of systems," Feigenbaum wrote in the blog post. "The system remains authorized while the changes are evaluated by the GSA."
"We've been very transparent about our FISMA authorization," he wrote. "Our documentation has always been readily available for any government agency to review, and dozens of officials from a range of departments and agencies have availed themselves of the opportunity to learn more about how we keep our customers' data secure.
"We'll continue to update our documentation to reflect new capabilities in Google Apps," he wrote.
Microsoft did not immediately reply to a request for comment on Google's blog post.