Heartbleed certificate revocation tsunami yet to arrive

Only 30,000 of the 500,000+ SSL certificates affected by the Heartbleed bug have been reissued up until today, and even fewer certificates have been revoked.


There has been a noticeable rise in certificate re-issuance since 7 April 2014

Some of the first sites to deploy newly issued certificates in response to the OpenSSL vulnerability included Yahoo, Adobe, CloudFlare, DuckDuckGo, GitHub, Reddit , Launchpad, PayPal, Netflix and Amazon's CloudFront content delivery network.

Such is the haste to fix the fallout of the Heartbleed bug, some certificate authorities and website administrators have been making careless mistakes. PayPal's Hosted Message Applications, such as the one at https://view.paypal-communication.com, are now using Extended Validation certificates issued by VeriSign on 10 April 2014. The CAB Forum requires certificate authorities to adhere to a stringent set of guidelines [pdf] when issuing EV certificates, and it is the CA's responsibility to verify the accuracy of the information in the certificate. In particular, they must verify that the legal name of the subject in an EV certificate matches the name which appears on official government records.

However, this verification does not appear to have been performed correctly in the case of these certificates, as they have been erroneously issued to an organisation named "PayPal, Inc.\0a" instead of "PayPal, Inc."


Extended Validation certificates cause browsers to display a green dialog, indicating the additional — and supposedly more accurate — identify verification criteria.

If you don't revoke your certificate, you may still be vulnerable to impersonation

If your private key has been stolen, just reissuing the certificate is not enough to mitigate the risks posed by the Heartbleed bug. Websites which were affected by the bug could still be vulnerable to impersonation attacks in the future if they fail to revoke their certificates, even if they have upgraded to the latest version of OpenSSL and replaced their SSL certificates.

If a remote attacker successfully retrieved private keys from a server while it was still vulnerable to the Heartbleed bug, then he would be able to impersonate the server by creating his own valid SSL certificate. The crucial issue is that an attacker can still do this after the affected website has upgraded to the latest version of OpenSSL, and it does not matter whether the real website has since deployed a new SSL certificate with different keys: Unless the previous certificate is revoked, the site will still be vulnerable to man-in-the-middle attacks.


Certificate revocations have gone up, but most of the vulnerable certificates are yet to be revoked.

Despite the importance of revoking certificates which could have been stolen using the Heartbleed bug, many website administrators and certificate authorities have yet to do this. Activity on certificate revocation lists peaked at a rate of 3,900 revocations per hour on the day the Heartbleed bug was announced (Monday April 7, 2014). On a typical Monday, we would expect to see a total of around 22,000-30,000 SSL certificates being revoked over the course of the day. On the Monday that the Heartbleed bug was announced to the public, there were 29,000 revocations. On the next day (Tuesday), 33,000 certificates were revoked, followed by 32,000 on Wednesday. These were both above average, suggesting that around 5,000 certificates were revoked in direct response to the Heartbleed bug each day. Note that fewer revocations usually take place over weekends.

Certificate authorities must revoke certificates within 24 hours if there is evidence of a key compromise. A private key is said to be compromised if its value has been disclosed, or if there exists a practical technique by which an unauthorised person may discover its value. Arguably, all certificates on sites vulnerable to the Heartbleed bug should be revoked by now, as such a technique was successfully carried out by the researchers behind heartbleed.com.

Even if you revoke your certificate, you may still be vulnerable to impersonation

However, even if all of the affected certificates were to be revoked, contemporary web browser software handles certificate revocation poorly. The most frequent users of a site — often its administrators — can continue using a revoked certificate for weeks or months without the browser notifying them that anything is amiss. In this situation, an attacker can perform a man-in-the-middle (MITM) attack by presenting the certificate to unsuspecting users whose browsers will behave as if they were connecting to the legitimate site. For example, some browsers only perform OCSP revocation checks for Extended Validation certificates, while others ignore certificate revocation lists completely.

You are encouraged to read our previous article on certificate revocation.

Since this article was first published, the revocation data has been updated to include more events.

Half a million widely trusted websites vulnerable to Heartbleed bug

A serious overrun vulnerability in the OpenSSL cryptographic library affects around 17% of SSL web servers which use certificates issued by trusted certificate authorities. Already commonly known as the Heartbleed bug, a missing bounds check in the handling of the TLS heartbeat extension can allow remote attackers to view up to 64 kilobytes of memory on an affected server. This could allow attackers to retrieve private keys and ultimately decrypt the server's encrypted traffic or even impersonate the server.

The Heartbleed bug write-up mentions Apache and nginx as being the most notable software using OpenSSL, and also points out that these have a combined active site market share of over 66% according to our April 2014 Web Server Survey. However, not all of these servers are running an HTTPS service, nor are they all running vulnerable versions of OpenSSL with heartbeats enabled.

Our most recent SSL Survey found that the heartbeat extension was enabled on 17.5% of SSL sites, accounting for around half a million certificates issued by trusted certificate authorities. These certificates are consequently vulnerable to being spoofed (through private key disclosure), allowing an attacker to impersonate the affected websites without raising any browser warnings.


Most vulnerable servers are using Apache.

Note that a small percentage of Microsoft web servers also appear to support the TLS heartbeat extension; these are actually likely to be vulnerable Linux machines acting as reverse proxy frontends to Windows servers.

Support for heartbeats was added to OpenSSL 1.0.1 (released in 2012) by Robin Seggelmann, who also coauthored the Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension RFC. The new code was committed to OpenSSL's git repository just before midnight on new year's eve 2011.

OpenSSL's security advisory states that only versions 1.0.1 and 1.0.2-beta are affected, including 1.0.1f and 1.0.2-beta1. The vulnerability has been fixed in OpenSSL 1.0.1g, and users who are unable to upgrade immediately can disable heartbeat support by recompiling OpenSSL with the -DOPENSSL_NO_HEARTBEATS flag.

Popular sites which exhibit support for the TLS heartbeat extension include Twitter, GitHub, Yahoo, Tumblr, Steam, DropBox, HypoVereinsbank, PostFinance, Regents Bank, Commonwealth Bank of Australia, and the anonymous search engine DuckDuckGo.

Certificates and keys at risk of compromise should be revoked and replaced, particularly if they are used to protect sensitive data. Certificate Authorities, hosting companies and other interested parties can contact us for assistance in identifying affected certificates.

You can check whether your own HTTPS website might be vulnerable using the form below, and looking for the RFC6520 heartbeat TLS extension.

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Thousands of websites still hosted on Windows XP

Thousands of websites are still hosted on Windows XP computers, despite the operating system reaching the end of its extended support period today. After today, Microsoft will stop providing automatic security updates for Windows XP, and Microsoft Security Essentials will also no longer be available for Windows XP.

Originally released in 2001, Windows XP is currently used by more than 6,000 websites in Netcraft's April 2014 Web Server Survey. Although China is often regarded as one of the most prolific users of Windows XP, only 3% of these sites are hosted there, suggesting that Windows XP has a predominantly desktop role in China. The largest share (nearly a third) of all Windows XP-powered websites are actually hosted in the United States.

Distribution of Windows XP-powered websites (logarithmic scale)

Notably, there are 14 US government websites still running on Windows XP, including a webmail system used by the State of Utah. Unsupported web-facing Windows XP servers are likely to become prime targets for hackers, particularly if any new Windows XP vulnerabilities are discovered, as no security updates will be available to fix them.  To afford some breathing space, the UK Government recently struck a £5.5m deal for Microsoft to provide it with an extra year of support for Windows XP, although there are currently no Windows XP-powered websites under the gov.uk top-level domain.

One of the busiest sites still using Windows XP is TransFerry.com. This site was previously using Windows 2000, and perhaps more worrying is the significantly larger number of websites which still use Windows 2000. This version of Windows reached its extended support end date in July 2010, yet nearly half a million of today's websites are hosted on Windows 2000 servers, most of which are using the Microsoft IIS 5.0 web server software they were shipped with. This version of IIS is practically identical to that used by Windows XP (IIS 5.1).

Netcraft's April 2014 survey also found 50,000 websites which are hosted on even older Windows NT4 servers running Microsoft IIS 4.0, although three quarters of these sites are served from the same computer in Norway. One of the busiest sites still running on Windows NT4 is the Australian Postal Corporation's post.com.au, which has been using the same operating system for at least 13 years. Window NT4 and IIS 4.0 are also still used by Australia Post's Postbillpay bill payment service, airindia.co.in and by the French government's Ministère de l'Économie, des Finances et de l'Industrie.

.Aero Air Safety Site Hijacked

The website of the Agency for the Safety of Aerial Navigation in Africa and Madagascar (ASECNA) has been hijacked by hackers. Browsing to the site's homepage currently presents visitors with a PayPal phishing site, where visitors are asked to submit PayPal account details, including their password, address and credit card details. After entering these details, victims are redirected to the real PayPal website.


Visitors to the ASECNA homepage are automatically redirected to this phishy PHP script in the root directory.

ASECNA is responsible for managing 16 million square kilometers of airspace (1.5x the size of Europe), covering six flight information regions, but has yet to remove the phishing site from its own homepage. Netcraft detected and blocked the above PayPal phishing site on Tuesday, yet visitors to www.asecna.aero who ignore their browser's warnings are still being presented with the phishing content today (Friday). Comments within the source code suggest that the phishing site was designed by a man living in Salé, Morocco.

A second PayPal phishing site was also found in a subdirectory on the same server, but it has since been deleted. It is possible that it was deleted by the fraudster behind the current attack, as it would be peculiar for ASECNA to have deleted phishing content from a subdirectory while leaving the more obvious phishing content on its homepage. The deleted phishing site used a phishing kit which hid its author's hotmail.fr email address in a Base64 encoded string. This made it less obvious to anyone deploying the kit that a duplicate copy of any stolen credentials would also be surreptitiously emailed directly to the kit's author. The phishing kit author's email address links him to a Facebook account which places him in Rabat, a Moroccan city which attracts many commuters from Salé. The same email address has been found in several other phishing kits, including some which target Visa customers.

It is rather unusual to see phishing sites hosted on .aero domains because they can only be registered by eligible members of the aviation community. SITA (an air transport IT and communications specialist) is responsible for verifying eligibility, and may ask applicants to provide company documents and pilot licenses, which reduces the likelihood of a fraudster registering a .aero domain specifically for the purpose of phishing. Many other top-level domains are easier to register, and some are even free.

 .aero is a sponsored top-level domain (sTLD). The original agreement for the domain was signed in 2001, and domains became available for registration in March 2002. In 2009, SITA signed a new 10-year sponsorship agreement for the .aero sTLD with ICANN.


How the ASECNA site looked prior to the compromise.

Netcraft's April 2014 survey found more than 9,000 sites using the .aero sTLD, and in the past 6 months they have hosted a total of 9 phishing sites. Each attack used an established .aero website which was compromised to host phishing content, rather than using a .aero domain registered specifically for fraud.

It is not apparent how the ASECNA website was compromised, although it appears to be running Apache 2.2.14, which could be vulnerable to a plethora of security issues which can be exploited remotely. The server also uses PHP 5.2.5, which was released in 2007, and the entire 5.2 branch of releases reached end of life status at the beginning of 2011. Unless the server is using a backporting approach to software maintenance, this old version of PHP could also expose a large number of vulnerabilities to remote attackers.

Netcraft's continuously updated, professionally validated phishing feed is used throughout the internet infrastructure industry. In addition to internet registries, all of the main web browsers, along with major anti-virus companies, firewall vendors, SSL Certificate authorities, large hosting companies and domain registrars use Netcraft's feed to protect their user communities. Please contact us for more information about these services, or about Netcraft's phishing site takedown service.

WordPress hosting: Do not try this at home!

Compromised WordPress blogs were used to host nearly 12,000 phishing sites in February. This represents more than 7% of all phishing attacks blocked during that month, and 11% of the unique IP addresses that were involved in phishing.

WordPress blogs were also responsible for distributing a significant amount of web-hosted malware — more than 8% of the malware URLs blocked by Netcraft in February were on WordPress blogs, or 19% of all unique IP addresses hosting malware.

WordPress is the most common blogging platform and content management system in the world: Netcraft's latest survey found nearly 27 million websites running WordPress, spread across 1.4 million different IP addresses and 12 million distinct domain names. Many of these blogs are vulnerable to brute-force password guessing attacks by virtue of the predictable location of the administrative interface and the still widespread use of the default "admin" username.

But remarkably, not a single phishing site was hosted on Automattic's own WordPress.com service in February. WordPress.com hosts millions of blogs powered by the open source WordPress software. Customers can purchase custom domain names to use for their blogs, or choose to register free blogs with hostnames like username.wordpress.com.

Automattic's founder, Matt Mullenweg, was one of the original authors of WordPress when it was released in 2003. Automattic later handed the WordPress trademark to the WordPress Foundation in 2010, but still contributes to the development of WordPress. Such familiarity with the product likely explains why blogs hosted at Automattic are significantly more secure than average.

Bloggers can also go it alone — anybody can download the WordPress software from wordpress.org and deploy it on their own website, and some hosting companies also offer "one-click" installations to simplify the process. Bloggers who install WordPress on their own websites will often also be responsible for keeping the software secure and up-to-date. Unfortunately, in many cases, they do not.

Even well-known security experts can fall victim to security flaws in WordPress if it is not their core activity. For example, in 2007, the Computer Security Group at the University of Cambridge found their own Light Blue Touchpaper blog had been compromised through several WordPress vulnerabilities.

Versions of WordPress after 3.7 are now able to automatically update themselves, provided the WordPress files are writable by the web server process. This has its own security trade-off, however, as an attacker exploiting a new and unreported vulnerability (a zero-day) that has the ability to write files will have free rein over the whole WordPress installation — an attacker could even modify the behaviour of WordPress itself to disable any future automatic security updates.

Insecure plugins

Over its lifetime, WordPress has been plagued by security issues both in its core code and in the numerous third-party plugins and themes that are available. One of the most widespread vulnerabilities this decade was discovered in the TimThumb plugin, which was bundled with many WordPress themes and consequently present on a large number of WordPress blogs. A subtle validation flaw made it possible for remote attackers to make the plugin download remote files and store them on the website. This allowed attackers to install PHP scripts on vulnerable blogs, ultimately facilitating the installation of malware and phishing kits. Similar vulnerabilities are still being exploited today.

Many of the phishing sites blocked in February were still operational this month, including this Apple iTunes phishing site hosted on a marketing company's website.

Dropzones for WordPress phishing content

Note that the above phishing content is stored in the blog's wp-includes directory, which is where the bulk of the WordPress application logic resides. More than a fifth of all phishing content hosted on WordPress blogs can be found within this directory, while another fifth resides in the wp-admin directory. However, the most common location is the wp-content directory, which is used by just over half of the phishing sites.

The wp-content directory is where WordPress stores user-supplied content, so it is almost always writable by the web server process. This makes it an obvious dropzone for malware and phishing content if a hacker is able to find and exploit a suitable vulnerability in WordPress, or indeed in any other web application running on the server. Shared hosting environments are particularly vulnerable if the file system permissions allow malicious users to write files to another user's wp-content directory. Some examples of directory structures used by phishing sites hosted in this directory on WordPress blogs include:

/wp-content/securelogin/webapps/paypal/
/wp-content/plugins/wordpress-importer/languages/image/Google/Google/
/wp-content/uploads/.1/Paypal/us/webscr.htm

The wp-includes and wp-admin directories can also be written to by other users or processes if the WordPress installation has not been suitably hardened. Failing to harden a WordPress installation and keep all of its plugins up to date could result in a site being compromised and used to carry out phishing attacks. Enabling automatic background updates is an easy way to ensure that a WordPress blog is kept up-to-date, but a significant trade off is that every WordPress file must be writable by the web server user.

Some other examples of directory structures seen in phishing sites hosted on WordPress blogs include:

/wp-includes/alibaba_online/
/wp-includes/www.paypal.com.fr.cgi.bin.webscr.cmd.login.submit.login/
/wp-includes/js/online.lloydsbank.co.uk/

/wp-admin/js/www.credit-mutuel.fr/
/wp-admin/maint/RBS-Card/index.html
/wp-admin/Googledoc/

Interestingly, the wp-admin directory appears to be the favourite location for Apple phishing sites – these make up more than 60% of all phishing sites found in this directory.

Vulnerable WordPress blogs can also be used for other nefarious purposes. A botnet of more than 162,000 WordPress blogs (less than 1% of all WordPress blogs) was recently involved in a distributed denial of service (DDoS) attack against a single website. Attackers exploited the Pingback feature in these WordPress blogs (which is enabled by default) to flood the target site with junk HTTP requests, causing it to be shut down by its hosting company.

A quarter of the phishing sites hosted on WordPress blogs in February targeted PayPal users, followed by 17% which targeted Apple customers.

Please contact us (sales@netcraft.com) for pricing or further details about any of our anti-phishing and web application security testing services.

EA Games website hacked to steal Apple IDs

An EA Games server has been compromised by hackers and is now hosting a phishing site which targets Apple ID account holders.

The compromised server is used by two websites in the ea.com domain, and is ordinarily used to host a calendar based on WebCalendar 1.2.0. This version was released in September 2008 and contains several security vulnerabilities which have been addressed in subsequent releases. For example, CVE-2012-5385 details a vulnerability which allows an unauthenticated attacker to modify settings and possibly execute arbitrary code. It is likely that one of these vulnerabilities was used to compromise the server, as the phishing content is located in the same directory as the WebCalendar application.

The phishing site attempts to trick a victim into submitting his Apple ID and password. It then presents a second form which asks the victim to verify his full name, card number, expiration date, verification code, date of birth, phone number, mother's maiden name, plus other details that would be useful to a fraudster. After submitting these details, the victim is redirected to the legitimate Apple ID website at https://appleid.apple.com/cgi-bin/WebObjects/MyAppleId.woa/

The compromised server is hosted within EA's own network. Compromised internet-visible servers are often used as "stepping stones" to attack internal servers and access data which would otherwise be invisible to the internet, although there is no obvious outward facing evidence to suggest that this has happened.

In this case, the hacker has managed to install and execute arbitrary PHP scripts on the EA server, so it is likely that he can at least also view the contents of the calendar and some of the source code and other data present on the server. The mere presence of old software can often provide sufficient incentive for a hacker to target one system over another, and to spend more time looking for additional vulnerabilities or trying to probe deeper into the internal network.

As well as hosting phishing sites, EA Games is also the target of phishing attacks which try to steal credentials from users of its Origin digital distribution platform. For example, the following site — which has been online for more than a week — is attempting to steal email addresses, passwords and security question answers.

EA's Origin servers also came under attack earlier this year, causing connectivity and login problems in various EA games. A tweet by @DerpTrolling appeared to claim responsibility for the outages, while also suggesting that it was a distributed denial of service attack which caused the problems.

("Gaben" is a reference to Gabe Newell, managing director of Valve Corporation, which owns the competing Steam digital distribution platform)

Netcraft has blocked access to all phishing sites mentioned in this article, and informed EA yesterday that their server has been compromised. However, the vulnerable server — and the phishing content — is still online at the time of publication.

The Audited by Netcraft service provides a means of regularly testing internet infrastructure for old and vulnerable software, faulty configurations, weak encryption and other issues which would fail to meet the PCI DSS standard. These automated scans can be run as frequently as every day, and can be augmented by Netcraft's Web Application Security Testing service, which provides a much deeper manual analysis of a web application by an experienced security professional.