Internet Information Services is an extensible web server created by Microsoft for use with
Windows NT family.
IIS supports HTTP, HTTPS, FTP, FTPS, SMTP and NNTP.
It has been an integral part of the Windows NT family since Windows NT 4.0, though it
may be absent from some editions.
IIS is not turned on by default when Windows is installed.
The IIS Manager is accessed through the Microsoft Management Console or Administrative Tools
in the Control Panel.
History The first Microsoft web server was a research
project at the European Microsoft Windows NT Academic Centre, part of the University
of Edinburgh in Scotland, and was distributed as freeware.
However, since the EMWAC server was unable to scale to handle the volume of traffic going
to Microsoft.com, Microsoft was forced to develop its own web server, IIS.
Almost every version of IIS was released either alongside or with a version of Microsoft Windows:
IIS 1.0 was initially released as a free add-on for Windows NT 3.51.
IIS 2.0 was included with Windows NT 4.0.
IIS 3.0, which was included with Service Pack 2 of Windows NT 4.0, introduced the Active
Server Pages dynamic scripting environment.
IIS 4.0 was released as part of an "Option Pack" for Windows NT 4.0.
IIS 5.0 shipped with Windows 2000 and introduced additional authentication methods, management
enhancements including a new MMC-based administration application, support for the WebDAV protocol,
and enhancements to ASP.
IIS 5.0 also dropped support for the Gopher protocol
IIS 5.1 was shipped with Windows XP Professional, and was nearly identical to IIS 5.0 on Windows
2000.
IIS 6.0, included with Windows Server 2003 and Windows XP Professional x64 Edition, added
support for IPv6 and included a new worker process model that increased security as well
as reliability.
IIS 7.0 was a complete redesign and rewrite of IIS, and was shipped with Windows Vista
and Windows Server 2008.
IIS 7.0 included a new modular design that allowed for a reduced attack surface and increased
performance.
It also introduced a hierarchical configuration system allowing for simpler site deploys,
a new Windows Forms-based management application, new command-line management options and increased
support for the .NET Framework.
IIS 7.0 on Vista does not limit the number of allowed connections as IIS on XP did, but
limits concurrent requests to 10 or 3.
Additional requests are queued, which hampers performance, but they are not rejected as
with XP.
IIS 7.5 was included in Windows 7 and Windows Server 2008 R2.
IIS 7.5 improved WebDAV and FTP modules as well as command-line administration in PowerShell.
It also introduced TLS 1.1 and TLS 1.2 support and the Best Practices Analyzer tool and process
isolation for application pools.
IIS 8.0 is only available in Windows Server 2012 and Windows 8.
IIS 8.0 includes Application Initialization, centralized SSL certificate support, and multicore
scaling on NUMA hardware, among other new features.
IIS 8.5 is included in Windows Server 2012 R2 and Windows 8.1.
This version includes Idle worker-Process page-out, Dynamic Site Activation, Enhanced
Logging, ETW logging, and Automatic Certificate Rebind.
All versions of IIS prior to 7.0 running on client operating systems supported only 10
simultaneous connections and a single website.
Microsoft was criticized by vendors of other Web server software, including O'Reilly & Associates
and Netscape Communications Corp., for its licensing of early versions of Windows NT;
the "Workstation" edition of the OS permitted only ten simultaneous TCP/IP connections,
whereas the more expensive "Server" edition, which otherwise had few additional features,
permitted unlimited connections but bundled IIS.
It was inferred that this was intended to discourage consumers from running alternative
Web server packages on the cheaper edition.
Netscape wrote an open letter to the Antitrust Division of the U.S. Department of Justice
regarding this distinction in product licensing, which it asserted had no technical merit.
Features IIS 6.0 and higher support the following authentication
mechanisms: Anonymous authentication
Basic access authentication Digest access authentication
Integrated Windows Authentication UNC authentication
.NET Passport Authentication Certificate authentication
IIS 7.0 has a modular architecture.
Modules, also called extensions, can be added or removed individually so that only modules
required for specific functionality have to be installed.
IIS 7 includes native modules as part of the full installation.
These modules are individual features that the server uses to process requests and include
the following: Security modules: Used to perform many tasks
related to security in the request-processing pipeline, such as specifying authentication
schemes, performing URL authorization, and filtering requests.
Content modules: Used to perform tasks related to content in the request-processing pipeline,
such as processing requests for static files, returning a default page when a client does
not specify a resource in a request, and listing the contents of a directory.
Compression modules: Used to perform tasks related to compression in the request-processing
pipeline, such as compressing responses, applying Gzip compression transfer coding to responses,
and performing pre-compression of static content.
Caching modules: Used to perform tasks related to caching in the request-processing pipeline,
such as storing processed information in memory on the server and using cached content in
subsequent requests for the same resource.
Logging and Diagnostics modules: Used to perform tasks related to logging and diagnostics in
the request-processing pipeline, such as passing information and processing status to HTTP.
sys for logging, reporting events, and tracking requests currently executing in worker processes.
IIS 7.5 includes the following additional or enhanced security features:
Client certificate mapping IP security
Request filtering URL authorization
Authentication changed slightly between IIS 6.0 and IIS 7, most notably in that the anonymous
user which was named "IUSR_{machinename}" is a built-in account in Vista and future
operating systems and named "IUSR".
Notably, in IIS 7, each authentication mechanism is isolated into its own module and can be
installed or uninstalled.
IIS 8.0 offers new features targeted at performance and easier administration.
The new features are: Application Initialization: a feature that
allows an administrator to configure certain applications to start automatically with server
startup.
This reduces the wait time experiences by users who access the site for the first time
after a server reboot.
Splash page during application initialization: the administrator can configure a splash page
to be displayed to the site visitor during an application initialization.
ASP.net 4.5 support: With IIS 8.0, ASP.net 4.5 is included by default, and IIS also offers
several configuration options for running it side-by-side with ASP.net 3.5.
Centralized SSL certificate support: a feature that makes managing certificates easier by
allowing the administrator to store and access the certificates on a file share.
Multicore scaling on NUMA hardware: IIS 8.0 provides several configuration options that
optimize performance on systems that run NUMA, such as running several worker processes under
one application pool, using soft or hard affinity and more.
WebSocket Protocol Support Server Name Indication: SNI is an extension
to Transport Layer Security, which allows binding of multiple websites with different
hostnames to one IP address.
Dynamic IP Address Restrictions: a feature that enables an administrator to dynamically
block IPs or IP ranges that hit the server with a large number of requests
CPU Throttling: a set of controls that allow the server administrator to control CPU usage
by each application pool in order to optimize performance in a multi-tenant environment
IIS 8.5 has several improvements related to performance in large-scale scenarios, such
as those used by commercial hosting providers and Microsoft's own cloud offerings.
It also has several added features related to logging and troubleshooting.
The new features are: Idle worker-Process page-out: a function to
suspend idle site to reduce the memory footprint of idle sites
Dynamic Site Activation: a feature that registers listening queues only to sites that have received
requests Enhanced Logging: a feature to allow collection
of Server variables, request headers and response headers in the IIS logs
ETW logging: an ETW provider which allows collecting real-time logs using various Event-tracing
tool Automatic Certificate Rebind: a feature that
detects when a site certificate has been renewed, and automatically rebinds the site to it
IIS Express IIS Express, a lightweight version of IIS,
is available as a standalone freeware server and may be installed on Windows XP with Service
Pack 3 and subsequent versions of Microsoft Windows.
IIS 7.5 Express supports only the HTTP and HTTPS protocols.
IIS Express can be downloaded separately or as a part of WebMatrix.
Extensions IIS releases new feature modules between major
version releases to add new functionality.
The following extensions are available for IIS 7.5:
FTP Publishing Service: Lets Web content creators publish content securely to IIS 7 Web servers
with SSL-based authentication and data transfer.
Administration Pack: Adds administration UI support for management features in IIS 7,
including ASP.NET authorization, custom errors, FastCGI configuration, and request filtering.
Application Request Routing: Provides a proxy-based routing module that forwards HTTP requests
to content servers based on HTTP headers, server variables, and load balance algorithms.
Database Manager: Allows easy management of local and remote databases from within IIS
Manager.
Media Services: Integrates a media delivery platform with IIS to manage and administer
delivery of rich media and other Web content.
URL Rewrite Module: Provides a rule-based rewriting mechanism for changing request URLs
before they are processed by the Web server.
WebDAV: Lets Web authors publish content securely to IIS 7 Web servers, and lets Web administrators
and hosters manage WebDAV settings using IIS 7 management and configuration tools.
Web Deployment Tool: Synchronizes IIS 6.0 and IIS 7 servers, migrates an IIS 6.0 server
to IIS 7, and deploys Web applications to an IIS 7 server.
Usage According to Netcraft, on 13 February 2014,
IIS is the second most popular web server in the world, behind Apache HTTP Server with
a market share of 32.80%.
It shows an increase of 3.38% in comparison to the previous month.
Netcraft shows a rising trend in market share for IIS, since 2012.
A day later, however, the W3Techs shows different results.
According to W3Techs, IIS is the third most used web server behind Apache HTTP Server
and Nginx.
Furthermore, it shows a consistently falling trend for IIS use since February 2013.
Security Earlier versions of IIS were hit with a number
of vulnerabilities, especially the CA-2001-13 which led to the infamous Code Red worm; however,
both versions 6.0 and 7.0 currently have no reported issues with this specific vulnerability.
In IIS 6.0 Microsoft opted to change the behaviour of pre-installed ISAPI handlers, many of which
were culprits in the vulnerabilities of 4.0 and 5.0, thus reducing the attack surface
of IIS.
In addition, IIS 6.0 added a feature called "Web Service Extensions" that prevents IIS
from launching any program without explicit permission by an administrator.
By default IIS 5.1 and lower run websites in-process under the SYSTEM account, a default
Windows account with 'superuser' rights.
Under 6.0 all request handling processes have been brought under a Network Services account
with significantly fewer privileges so that should there be a vulnerability in a feature
or in custom code it won't necessarily compromise the entire system given the sandboxed environment
these worker processes run in.
IIS 6.0 also contained a new kernel HTTP stack with a stricter HTTP request parser and response
cache for both static and dynamic content.
According to Secunia, as of June 2011, IIS 7 had a total of 6 resolved vulnerabilities
while IIS 6 had a total of 11 vulnerabilities out of which 1 was still unpatched.
The unpatched security advisory has a severity rating of 2 out of 5.
In June 2007, a Google study of 80 million domains concluded that while the IIS market
share was 23% at the time, IIS servers hosted 49% of the world's malware, the same as Apache
servers whose market share was 66%.
The study also observed the geographical location of these dirty servers and suggested that
the cause of this could be the use of pirated copies of Windows that could not obtain security
updates from Microsoft.
In a blog post on 28 April 2009, Microsoft noted that it supplies security updates to
everyone without genuine verification.
The 2013 mass surveillance disclosures made it more widely known that IIS is particularly
bad in supporting perfect forward secrecy, especially when used in conjunction with Internet
Explorer.
Possessing one of the long term asymmetric secret keys used to establish a HTTPS session
should not make it easier to derive the short term session key to then decrypt the conversation,
even at a later time.
Diffie–Hellman key exchange and Elliptic curve Diffie–Hellman key exchange are in
2013 the only ones known to have that property.
Only 30% of Firefox, Opera, and Chromium Browser sessions use it, and nearly 0% of Apple's
Safari and Microsoft Internet Explorer sessions.
See also WISA
IIS Metabase Logparser
Microsoft Personal Web Server Windows Activation Services
Comparison of web servers List of mail servers
References
External links Official website
IIS on Server and Cloud Platform portal Security Guidance for IIS on TechNet