What is the 'Heartbleed' bug?
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 users.
What does this mean for web sites in general?
The nature of the Heartbleed Bug and the fact that is has been afflicting web servers since 2011 means that in the absolute worst case scenario, all data on afflicted sites could have been accessed by unauthorized persons. This would be accomplished by using the Heartbleed Bug to retrieve the private key from an afflicted web server, capturing the HTTPS traffic, using the captured private key to decrypt the captured HTTPS traffic and then either using any contained passwords to gain unauthorized access to the site or using the data itself elsewhere (ie. credit card data).