More than 600,000 web-facing computers — which host millions of websites — are still running Windows Server 2003, despite it no longer being supported.

Extended support for Windows Server 2003 ended on July 14, 2015. Crucially, this means that Microsoft will no longer be issuing security updates for any version of Windows Server 2003. US-CERT warns that these unsupported installations of Windows Server 2003 are exposed to an elevated risk of cybersecurity dangers, such as malicious attacks or electronic data loss.

Windows Server 2003 was originally launched over 12 years ago, with the latest major update being released 8 years ago in the form of Service Pack 2. This update was particularly beneficial for web servers, as it added the Scalable Networking Pack (SNP), which allowed for hardware acceleration of network packet processing.

Fifth of the internet still running Windows Server 2003

Netcraft's July 2015 Web Server Survey found 175 million websites that are served directly from Windows Server 2003 computers. These account for more than a fifth of all websites in the survey, making the potential attack surface huge.

Most of these sites (73%) are served by Microsoft Internet Information Services 6.0, which is the version of IIS that shipped with Windows Server 2003 and the 64-bit edition of Windows XP Professional; however, it is rare to see the latter being used as a web server platform.

The remaining Windows Server 2003-powered sites use a variety of web server software, with GSHD 3.0, Safedog 4.0.0, Apache 2.2.8 (Win32), kangle 3.4.8, NetBox Version 2.8 Build 4128 and nginx/1.0.13-win32 being amongst the most commonly seen Server headers. While vulnerabilities in these software products can be addressed by applying patches or updates, future vulnerabilities in the underlying Windows Server 2003 operating system may never be fixed.

14 million of the sites did not send a Server header at all, so it was not apparent whether the web server software used by these sites could be updated, but the underlying computers could still be identified as running Windows Server 2003. Netcraft determines the operating system of a remote web server by analysing the low-level TCP/IP characteristics of response packets, and so it is independent of whichever server software the site claims to be running.

Backend servers might also be exploitable

In addition to the 175 million websites that are served directly from Windows Server 2003 computers, a further 1.7 million sites served from other operating systems sent the Microsoft-IIS/6.0 Server header. This indicates the presence of backend Windows Server 2003 machines behind load balances and similar devices that are not running Windows.

For example, if the TCP/IP characteristics of a web server's response indicate that it is running Linux, but the HTTP Server header reports it is using Microsoft-IIS/6.0, then the Linux machine is likely to be acting as a reverse proxy to a Windows Server 2003 machine running IIS 6.0. Although the Windows Server 2003 machine is not directly exposed to the internet, it may still be possible for a remote attacker to exploit certain Windows and IIS vulnerabilities.

How many Windows Server 2003 installations are exposed to the web?

Netcraft has developed a technique for identifying the number of unique computers that act as web servers on the internet. The 175 million sites that use Windows Server 2003 make use of 1.6 million distinct IP addresses. However, an individual computer running Windows Server 2003 may have multiple IP addresses, which makes this an unsuitable metric for determining how many installations there are.

Further analysis of the low-level TCP/IP characteristics reveals a total of 609,000 web-facing computers running Windows Server 2003. This is over 10% of all web-facing computers, and shows the true potential cost of migration, as software licensing is typically charged on a per-machine rather than per-IP address basis.

Who's still using Windows Server 2003?

China and the United States account for 55% of the world's Windows Server 2003 computers (169,000 in China and 166,000 in the US), yet only 43% of all other web facing computers.

Within China, more than 24,000 of these computers are hosted by Alibaba Group. Nearly half of these are hosted by HiChina, which was acquired by Alibaba in 2009, while 7,500 are hosted at its rapidly growing cloud hosting unit, Aliyun.

One of the most prominent companies still using Windows Server 2003 on the internet is LivePerson, which is best known for the live chat software that allows its customers to talk to their visitors in realtime. Its main site at www.liveperson.com uses Microsoft IIS 6.0 on Windows Server 2003, and several other sites related to its live chat functionality — such as sales.liveperson.net — also appear to use IIS 6.0 on Server 2003, but are served via F5 BIG IP web-facing devices.

Even some banks are still using Windows Server 2003 and IIS 6.0 on their main sites, with the most popular ones including Natwest, ANZ, and Grupo Bancolombia. These sites rank amongst the top 10,000 in the world, and hundreds of other banking sites also appear to be using Windows Server 2003.

ING Direct and Caisse d'Epargne are also using IIS 6.0, but these sites appear to be served through F5 BIG-IP or similar devices, rather than having Windows Server 2003 machines exposed directly to the internet. Even some security and antivirus software vendors are still running IIS 6.0 on public-facing sites, including Panda Security and eScan.

While Microsoft does not officially offer any support beyond the extended support period ("Once a product transitions out of support, no further support will be provided for the product"), reports suggest that some companies who have not migrated in time have arranged to pay millions of dollars for custom support deals.

PCI compliance: Automatic failure

Companies still using unsupported operating systems like Windows Server 2003 in a cardholder data environment should migrate immediately. All organisations and merchants who accept, transmit or store cardholder data must maintain a secure PCI compliant environment.

The Payment Card Industry Data Security Standard (PCI DSS) provides a baseline of technical and operational requirements designed to protect cardholder data and sensitive authentication data. PCI DSS Requirement 6.2 requires all system components and software to be protected from known vulnerabilities by installing vendor-supplied security patches. This will not be possible with Windows Server 2003, as no more security updates will be made available by Microsoft.

Additionally, merchants and service providers who handle a large enough volume of cardholder data must have quarterly security scans by a PCI SSC Approved Scanning Vendor (such as Netcraft) in order to maintain compliance. ASVs are required to record an automatic failure if the merchant's cardholder data environment uses an operating system that is no longer supported.

In some cases, the PCI SSC can allow for risks to be mitigated through the implementation of suitable compensating controls, but these are unlikely to be sufficient for an unsupported web-facing operating system – especially one which will become less secure as time goes by, as new vulnerabilities are discovered.

Consequently, many merchants still using Windows Server 2003 is likely to be noncompliant, and could face fines, increased transaction fees, reputational damage, or other potentially disastrous penalties such as cancelled accounts.

Microsoft advises that any datacenter still using Windows Server 2003 needs to protect its infrastructure by planning and executing a migration strategy. Some possible options suggested by Microsoft include switching to Windows Server 2012 R2, Microsoft Azure or Office 365. To help customers migrate, Microsoft has provided an interactive Windows Server 2003 Migration Planning Assistant, which, incidentally, is hosted on Microsoft Azure.

Finding out more

Netcraft's techniques provide an independent view with a consistent methodology on the number of web-facing computers at each hosting location worldwide. For more information, see our Hosting Provider Server Count, or contact us at sales@netcraft.com for bespoke datasets.

For more information about Netcraft's Automated Vulnerability Scanning for PCI Compliance, please contact us at security-sales@netcraft.com.