Counting SSL certificates

The SSL/TLS protocol — used to protect sensitive communication across the internet — combines encryption with authentication, providing a private connection to the intended recipient. To achieve this, SSL certificates bind together a cryptographic key and a domain name, and are digitally-signed by a trusted certificate authority (CA). Commercial CAs compete to sell certificates to the general public and account for the bulk of the SSL certificates seen on the internet.

Netcraft's SSL Server Survey has been running since 1996 and has tracked the evolution of this marketplace from its inception — there are now more than one thousand times more certificates on the web now than in 1996. As CAs issue certificates, and most charge (or not charge) accordingly, the number of certificates issued becomes the natural unit of measurement. Our survey therefore counts valid, trusted SSL certificates used on public-facing web servers, counting each certificate once, even if used on multiple websites.

certs

Two types of certificates make the distinction between counting sites and certificates most apparent: multi-domain certificates and wildcard certificates. These two types now account for almost a quarter of all certificates found.

  • Multi-domain certificates (or UCC certificates) use the Subject Alternative Name extension to specify additional hostnames for which this certificate is valid — CloudFlare uses this technique heavily, having dozens of unrelated sites share the same certificate.
  • Wildcard certificates are valid for all possible subdomains of a domain, for example *.netcraft.com would be valid for www.netcraft.com, host-a.netcraft.com, host-b.netcraft.com, etc. Our methodology counts a wildcard certificate once, no matter the number of sites for which it is valid.

Netcraft also counts certificates used by subdomains. For example, if foo.example.com, bar.example.com and baz.example.com are all using different SSL certificates, Netcraft will count all three certificates that have been issued.

Although the global SSL ecosystem is competitive, it is dominated by a handful of major CAs — three certificate authorities (Symantec, Comodo and GoDaddy) account for three-quarters of all issued SSL certificates on public-facing web servers. The top spot has been held by Symantec (or VeriSign before it was purchased by Symantec) ever since the survey began, with it currently accounting for just under a third of all certificates. To illustrate the effect of differing methodologies, amongst the million busiest sites Symantec issued 44% of the valid, trusted certificates in use — significantly more than its overall market share.

However, nothing ever stays still forever — Let's Encrypt could shake up the market for SSL certificates later on this year by offering free certificates with a simplified installation process. Whilst free certificates and automated tools are nothing new, the open approach and the backing of Mozilla, IdenTrust, the EFF, and Akamai could change the SSL ecosystem forever.

Beyond counting certificate numbers, Netcraft's SSL Survey also tracks the list and reseller prices of the most popular certificate authorities. This provides another useful market share metric, as it allows us to estimate the total monthly and annual revenue of each certificate authority attributable to public SSL issuance.

As each type of certificate — multi-domain, wildcard, or Extended Validation for example — is available at a distinct price point, the estimated revenue of a CA can vary significantly, despite initially appearing similarly sized by the total number of certificates. For example, GlobalSign comes in third-place when considering its estimated annual revenue (by list price) in 2014, despite accounting for approximately 6% of all currently valid publicly-visible SSL certificates.

For additional information or details on how to purchase Netcraft’s SSL Server Survey please contact us at sales@netcraft.com or visit our web site.

Instagram forgets to renew its SSL certificate

Instagram's SSL certificate expired at midday GMT on Thursday 30th April 2015 and was not replaced for more than an hour, leaving visitors unable to access the site without seeing browser warnings.

Browser warnings caused by Instagram's expired SSL certificate.

Browser warnings caused by Instagram's expired SSL certificate.

The expired DigiCert-issued certificate that was being served from https://instagram.com/ has now been replaced with a different certificate, valid until 15th October 2015.

Users who ignore the warnings from their browser could be at risk of man-in-the-middle attacks, where a correctly-positioned attacker can surreptitiously steal usernames, passwords and session cookies without the victim's knowledge.

Although the HTTP version of the site redirects to HTTPS, instagram.com does not currently make use of HTTP Strict Transport Security — an HTTP header that permits a site to specify that future visits must be over HTTPS. As a result, customers can bypass the warning message, placing them at risk of man-in-the-middle attacks.

If HSTS had been in use, visitors would correctly not be able to bypass the error message, protecting them from man-in-the-middle attacks, but leaving them without the ability to connect to instagram.com. As HSTS does not protect the user on their first visit, website owners can request to have their HSTS rules embedded into the browser via Chrome's preload list.

instagram-cert-error

The SSL error message in Google Chrome can be bypassed for instagram.com (which does not use HSTS).

paypal-cert-error

In simulating an attack on www.paypal.com (which does use HSTS), Chrome's SSL error message cannot be bypassed.

instagram.com is the 310th most popular website amongst users of the Netcraft Toolbar. The Instagram app does not appear to be affected, as it makes use of a different server at i.instagram.com, which uses a valid certificate.

The SSL certificate used by instragram.com expired at midday UTC

The SSL certificate used by instagram.com expired at midday UTC

Hostinger hosts over 90% of all Steam phishing sites

Netcraft blocked more than 1,400 Steam phishing URLs last month, spread across 331 different websites. Surprisingly, more than 90% of these sites were hosted by just one company: Hostinger.

With more than 125 million active accounts, Steam continues to make an attractive target for fraudsters. The number of phishing attacks targeting Steam rose significantly last month, even though the fraudsters behind these attacks have had to change their tactics a few times. Last year, a popular ruse was to use Steam's own chat client to trick victims into visiting look-alike domain names similar to the genuine steamcommunity.com. This modus operandi continued into 2015, but became less effective after Steam started to remove suspicious links from chat messages.

Consequently, many Steam phishers have abandoned the idea of registering their own look-alike domains (only two were blocked last month), and are instead using subdomains provided by free hosting services such as Hostinger. These allow the fraudsters to host Steam phishing sites with addresses like steamcommuniity.hol.es, steampoweredssuport.esy.es and steamcomcoomity.16mb.com – not quite as convincing as the hostnames used in previous attacks, although the deliberate misspellings are similar.

A Steam phishing site hosted at steamcomcoomity.16mb.com

A Steam phishing site hosted by Hostinger at steamcomcoomity.16mb.com

Lithuania-based Hostinger provides many different second-level domains under which its customers can host a website, and the most common ones used in these attacks were esy.es, besaba.com, 16mb.com, wc.lt, hol.es and pe.hu.

Hostinger displays this content on each of its free hosting  domains. Hostinger covers its costs by offering paid upgrades for those who need  more resources.

Hostinger displays this content on each of its free hosting domains. Hostinger covers its costs by offering paid upgrades for those who need more resources.

Free hosting providers are an obvious choice for fraudsters who wish to carry out phishing attacks without leaving a financial trail. Hostinger's offerings look particularly conducive for phishing, as they do not display ads on their customers' sites, and they provide support for PHP (nearly all phishing kits are written in PHP).

Nonetheless, the incredible popularity of Hostinger within the Steam phishing arena is rather unusual. While Hostinger was used to host over 90% of all Steam phishing URLs, it hosted only 0.6% of all other phishing attacks that were blocked during March.

This preference of using Hostinger could suggest that the fraudsters behind most of these Steam phishing attacks are working together or copying each others' methodologies. In addition, there are examples of phishing sites that have remained up for long periods of time, which makes it an attractive hosting location for phishers. The hostname steamcomcoomity.16mb.com (shown in the earlier screenshot) has been serving a Steam phishing site from Hostinger's infrastructure since last year and is still serving it at the time of writing.

Netcraft provides a Phishing Alerts service for hosting providers and domain registrars who are unwittingly providing facilities for phishing. Brand owners can also use Netcraft's Takedown service to identify phishing attacks against them and get fraudulent sites shut down.

Google’s April Fool’s prank inadvertently broke their security

As part of its traditional series of April Fool's day jokes, Google used its own .google gTLD to launch a backwards version of its home page from the domain com.google on 1st April.

However, this year's joke inadvertently undermined an important security feature on Google's real homepage, which made it vulnerable to user interface redressing attacks such as click-jacking. This vulnerability would have allowed a remote attacker to change a user's search settings, including turning off SafeSearch filters.

The backwards content displayed on com.google

The backwards content displayed on com.google on 1 April 2015

The issue stemmed from the way com.google used an iframe to display backwards content from google.com. This would not normally be possible, as google.com uses the X-Frame-Options HTTP response header to prevent other websites from displaying itself within an iframe. But for the purpose of the April Fool's joke, Google stepped around this problem by passing the parameter "igu=2" to google.com, which not only told it to display the content backwards, but also instructed the server to omit the X-Frame-Options header entirely.

com.google uses an iframe to display a backwards search page from google.com. Also not the reversed text in the HTML comment, revealing that it is an April Fool's day joke.

com.google used an iframe to display a backwards search page from google.com. Also note the reversed text in the HTML comment.

A remote attacker could also have leveraged this "feature" to display the Google Search Settings page in an iframe on an external domain, and trick his victims into unwittingly changing those settings. A carefully constructed clickjacking attack could have gone unnoticed by each victim until it was too late and the settings had already been changed.

To highlight the different responses, the following was an ordinary response from Google's Search Settings page at https://www.google.com/preferences?hl=en&fg=1. Note the presence of the X-Frame-Options header:

HTTP/2.0 200 OK
Alternate-Protocol: 443:quic,p=0.5
Cache-Control: private
Content-Encoding: gzip
Content-Length: 35486
Content-Type: text/html; charset=UTF-8
Date: Wed, 01 Apr 2015 09:54:14 GMT
Expires: Wed, 01 Apr 2015 09:54:14 GMT
Server: gws
Set-Cookie: [redacted]
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Firefox-Spdy: h2-15

Conversely, with the igu=2 parameter appended, the X-Frame-Options header was omitted from the response, allowing the page to be displayed in a frame on an attacker's own website:

HTTP/2.0 200 OK
Alternate-Protocol: 443:quic,p=0.5
Cache-Control: private
Content-Encoding: gzip
Content-Length: 33936
Content-Type: text/html; charset=UTF-8
Date: Wed, 01 Apr 2015 09:58:30 GMT
Expires: Wed, 01 Apr 2015 09:58:30 GMT
Server: gws
Set-Cookie: [redacted]
X-XSS-Protection: 1; mode=block
X-Firefox-Spdy: h2-15
Google's Search Settings being successfully displayed within an iframe on a Netcraft domain

Google's Search Settings being successfully displayed within an iframe on a Netcraft domain on 1 April 2015 (this content is not served backwards).

Changes made to the above settings via the iframe would persist across the user's session when they subsequently used google.com in a normal window. Netcraft reported this issue to Google and it has since been resolved — the method described in this article can no longer be used to display the settings page within an iframe on an external domain.

Critical Windows vulnerability affects at least 70 million websites

The race is on to patch nearly a million Windows web servers, following the publication of code that can identify the presence of a serious vulnerability announced by Microsoft on Tuesday.

The critical vulnerability lies within Microsoft's HTTP protocol stack, known as HTTP.sys. The maximum security impact, according to Microsoft Security Bulletin MS15-034, is remote code execution — by sending a specially crafted HTTP request to a vulnerable server, a remote attacker can execute arbitrary code on that server.

An ongoing scan for this vulnerability suggests that the test performed by the published code is inconclusive, as it might erroneously give the all-clear to a server that returns non-static content, even if it is in fact vulnerable.

However, Netcraft's latest Web Server Survey shows more than 70 million websites could be vulnerable, including Microsoft IIS servers that sit behind non-Windows load balancers. The total number of servers involved in hosting these sites stands at around 900,000, which is more than a sixth of all web-facing computers in the world.

The affected versions of Windows includes Windows Server 2008 R2, 2012 and 2012 R2. Windows 7, 8 and 8.1 are also vulnerable, but are not commonly used to host websites. Microsoft's security bulletin does not include Windows Server 2003 in the list of affected versions, so the 130 million sites that run IIS 6.0 on this older operating system would appear to be safe (at least from this particular issue).

Given the swift publication of code that could potentially be developed into a practical exploit, it is essential that all Windows server administrators apply the necessary security updates as a matter of urgency.

Microsoft has already released a security update for this vulnerability, so don't delay, apply today!

Web security company inadvertently aids HMRC phishing attack

Web security company M86 Security Labs, which is now part of TrustWave SpiderLabs, is inadvertently helping fraudsters to carry out phishing attacks against HM Revenue & Customs.

The text within this HMRC phishing email is actually represented by a PNG image, which is loaded directly from the M86 Security Labs website.

The text within this HMRC phishing email is actually represented by a PNG image, which is loaded directly from the M86 Security Labs website.

The spoof emails involved in the ongoing attack look practically the same as many previous HMRC phishing emails — and that's because the content within the email body is being served directly from the M86 Security Labs website. The emails simply display a PNG screenshot of an email that was featured in a 2010 blog post by M86 Security Labs, which warned potential victims about an HMRC phishing attack.

Ironically, the screenshot featured in that blog post is now being used as a key component of the current attacks against taxpayers.

The HTML source of the email body.

The HTML source of the email body, which displays the 24kb image from the M86 blog post.

The image as it was intended to be shown on the M86 Security Labs blog.

The image as it was intended to be shown on the M86 Security Labs blog.

Clicking anywhere on the image in the phishing email takes the victim to an HMRC phishing site hosted in Turkey. This initially prompts the victim to enter their email address, full name and date of birth, before a subsequent page asks for even more information, including the victim's postal address and card details.

hmrc-phishingsite

Fake HMRC tax refunds remain a popular ruse. Netcraft blocked 1,150 HMRC phishing sites last month alone, and notably discovered one hosted under the trusted gov.uk domain in 2009.