The appointment follows a six-month search among the UK's most senior security professionals.
The position has been vacant since the departure of Stuart Okin, who left towards the end of last year after eight years in the role to take up a position with IT services firm Accenture.
Nick McGrath, head of platform strategy at Microsoft, said the appointment would be of key importance to IT departments in the UK. "This person is the number one person inside Microsoft in the UK when it comes to security. There is no one else," he said.
The security chief acts as a link between UK users and Microsoft. During his tenure, Okin personally phoned key Microsoft users to warn them when serious vulnerabilities were discovered in their operating systems.
Microsoft had originally hoped to announce Okin's replacement at the Infosecurity Europe conference last month. But finding a person with the right skills has not been easy, said McGrath.
"We have taken our time. It is important to make sure we have found the right individual with the right skill set, who is going to be happy to provide our customers with the information they need," he said.
One of the chief security adviser's key roles will be to work with Microsoft's business managers to gain feedback from users on the company's progress on security. They will also need to have an understanding of security vulnerabilities, best practices, technologies and Microsoft's business partners.
"Finding someone who has all the skills is hard to do. These things take time," said McGrath. "I have spoken to a number of the most gifted security professionals in and around the UK."
Ben Booth, chief executive of the BCS IT directors group Elite, said, "It is an important role. Given that security is so important, and because Microsoft is very much the focus of hackers, this is a crucial appointment."
Nick Marsh, head of the European technology practice at recruitment firm Harvey Nash, said Microsoft may have struggled to find someone to fill such a high profile role due to the pressure of the job. "Hackers are sitting in their bedrooms trying to break Microsoft code," he said. "You might as well just paint a target on yourself."