Heartbleed wasn't just an interesting Internet security story. It was a sign that one of the most fundamental building blocks relied on by many large companies was significantly flawed. Even more staggering was the revelation that the OpenSSL open source code library, that is responsible for SSL communications between systems, had another flaw that went undetected for over a decade.
OpenSSL is an open source code library. It is used by applications that use SSL and TLS to encrypt communications between systems. In simple terms, when communications are encrypted an application refers to the OpenSSL library to ensure that the communications have been correctly encrypted.
Unfortunately, there was a flaw in OpenSSL's logic that made it possible for a malicious party to access data that users thought was secured. This included private keys, session cookies and passwords.
Heartbleed is listed in the Common Vulnerabilities and Exposures system as CVE-2014-0160. This is a widely used system for tracking information security issues.
There's no doubt that Heartbleed is a significant issue but it is worth noting a few things. Not all SSL and TLS traffic is at risk. The Heartbleed issue is not the result of a bug in the SSL and TLS protocols.
So, only systems using OpenSSL are affected. These account for about 17% of the entire Internet making Heartbleed the most widespread security bug identified.
That means servers and applications running software made by Microsoft were not vulnerable to Heartbleed as they use a different code library for securing SSL and TLS communications.
Similarly, applications using GnuTLS and Mozilla's Network Security Services, are unaffected. And although Heartbleed was identified at about the same time as the Apple "GoTo Fail" bug, that was an unrelated flaw in Apple's SSL/TLS validation code.
Another bug in OpenSSL called the CCS Injection Vulnerability, designated CVE-2014-0224 in the OpenSSL bug tracking system, was identified in June 2014. Like Heartbleed, it affects one in every six servers on the Internet and, potentially hundreds of millions of users as OpenSSL is used by some of the most popular sites on the Internet. Incredibly, this flaw was present in OpenSSL for about 15 years.