The Heartbleed Bug is a serious vulnerability in the popular OpenSSL cryptographic software library. This weakness allows stealing the information protected, under normal conditions, by the SSL/TLS encryption used to secure the Internet. SSL/TLS provides communication security and privacy over the Internet for applications such as web, email, instant messaging (IM) and some virtual private networks (VPNs).

The Heartbleed bug allows anyone on the Internet to read the memory of the systems protected by the vulnerable versions of the OpenSSL software. This compromises the secret keys used to identify the service providers and to encrypt the traffic, the names and passwords of the users and the actual content. This allows attackers to eavesdrop on communications, steal data directly from the services and users and to impersonate services and user

Complete info here: http://heartbleed.com/s

The Heartbleed vulnerability in OpenSSL (CVE-2014-0160) has received a significant amount of attention recently. While the discovered issue is specific to OpenSSL, many customers are wondering whether this affects Microsoft’s offerings, specifically Windows and IIS.  Microsoft Account and Microsoft Azure, along with most Microsoft Services, were not impacted by the OpenSSL vulnerability. Windows’ implementation of SSL/TLS was also not impacted.

We also want to assure our customers that default configurations of Windows do not include OpenSSL, and are not impacted by this vulnerability.   Windows comes with its own encryption component called Secure Channel (a.k.a. SChannel), which is not susceptible to the Heartbleed vulnerability.

This applies to all Windows operating systems and IIS versions, up to and including IIS 8.5 running on any of the following operating systems:

•             Windows Server 2003 and 2003R2 
•             Windows Server 2008 
•             Windows Server 2008R2 
•             Windows Server 2012 
•             Windows Server 2012R2

Customers running software on Windows that uses OpenSSL instead of SChannel (for example, running the Windows version of Apache), may be vulnerable.  We recommend that all customers who may be vulnerable follow the guidance from their software distribution provider.  For more information and corrective action guidance, please see the information from US Cert here.

Source: http://blogs.technet.com/b/erezs_iis_blog/archive/2014/04/09/information-about-heartbleed-and-iis.aspx