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.
The following chart shows the number of vulnerable sites of Alexa’s top 10,000 sites over time. Such data can be gathered using the heartleed-masstest tool. The chart shows how fast (or slow) the different site owners react to patch their systems. There was no ongoing check between 2014-04-08 and 2014-04-09, which explains the gap in the chart.