The Netcraft Extension: Heartbleed and phishing protection rolled into one
The Heartbleed bug affected around 17% of all trusted SSL web servers when it was announced a week ago. The critical vulnerability in the OpenSSL cryptographic library has the potential to allow attackers to retrieve private keys and ultimately decrypt a server's encrypted traffic or even impersonate the server. This is not a theoretical problem: practical attacks have actually succeeded in stealing private keys, yet despite the potential dangers, many of the affected sites have yet to take remedial action.
Even if heartbeat support has been disabled, or OpenSSL upgraded to the latest version, a website that was previously vulnerable to Heartbleed is not necessarily secure today. If the vulnerability had been exploited prior to the upgrade, the certificate's private key could have been compromised. If the certificate has not yet been replaced and the old one revoked, an attacker could impersonate the site and carry out man-in-the-middle attacks against the site's visitors.
Netcraft's updated extensions for Chrome, Firefox and Opera now allow you to see whether the sites you visit are still using potentially compromised certificates. The extensions use data from Netcraft's SSL Survey to determine whether a site offered the heartbeat TLS Extension prior to the Heartbleed disclosure. If this is the case, the extension will also check to see if the site's SSL certificate has been replaced; if it has not, then the site is considered to be unsafe, as the certificate's private key could have been compromised. Even if the certificate has been replaced, it does not guarantee that the site cannot still be impersonated with a copy of the old certificate unless the old certificate has been revoked – and even then, the revocation checking done by browsers is not infallible.
Go here to download the Netcraft Extension for Chrome, Firefox or Opera.
The extension will indicate when a site is potentially unsafe by displaying a bleeding heart icon. Additionally, in the Google Chrome and Opera versions of the Extension, a warning triangle will be displayed on top of the Netcraft icon.
As well as indicating which sites are using a certificate potentially compromised using Heartbleed, the Netcraft Extension also helps protect you from phishing attacks, displays the hosting location and risk rating of every site you visit, and lets you help to defend the internet community against fraudsters.
Netcraft's site report pages can also be used to determine whether a website might still be affected by the fallout from the Heartbleed bug. For example, our site report for https://www.linkedin.com shows that it no longer supports the TLS heartbeat extension and is using a new certificate.
In contrast, the site report for https://www.fedex.com currently shows that the server previously supported TLS heartbeat and the SSL certificate has not been replaced. Even though TLS heartbeat is now disabled, the certificate could still be used to impersonate the site if it had been compromised prior to heartbeat being disabled. Fedex's website is hosted by Akamai, a popular Content Distribution Network, which was potentially vulnerable to Heartbleed. Akamai is in the process of rotating its customers' SSL certificates and stated that "some require extra validation with the certificate authorities and may take longer".
Heartbleed indicator in the Netcraft Site Report