Netcraft Extension Help Pages


A software program used to display pages from the World Wide Web. You are almost certainly using a browser to read this. Internet Explorer and Mozilla Firefox are the two most common browsers.
A document that is used to certify that a user or organisation is who they say they are. It contains information about who it belongs to, who it was issued by, expiry date and information that can be used to verify the contents of the certificate. It is as an important part of the SSL system for establishing secure connections.
DNS (Domain Name System)
The Domain Name System is a system of mapping Domain Names to IP addresses. Because domain names are alphabetic, they are easier for humans to remember. The Internet, however, is really based on IP addresses. Every time you use a Domain Name, DNS translates the name into the corresponding IP address. It is similar to a phonebook for the Internet.
Domain Name
The unique name that identifies an Internet site. Domain Names always have 2 or more parts, separated by dots. The part on the left is the most specific, and the part on the right is the most general. A given machine may have more than one Domain Name but a given Domain Name points to only one machine. For example, the domain names:

can all refer to the same machine, but each domain name can refer to no more than one machine.

Usually, all of the machines on a given network will have the same thing as the right-hand portion of their Domain Names ( in the examples above).

Electronic Mail (E-mail)
A method of electronically passing messages from one computer user to another, typically over the Internet.
An add-on program for a web browser that provides additional functionality to enhance web browsing. Some extensions create their own bar across the browser, usually positioned underneath the menu line. These are called toolbars.
A "hash function" is a mathematical formula that converts a message of any length into a fixed-length string of digits known as the "hash" that represents the original message. Hash functions are one-way - that is, it is infeasible to reverse the process to determine the original message. Hash functions such as MD5 are strongly collision-free, which means it is very difficult to find two messages that produce the same hash.
IP Address
The address which provides a unique identification of a server and the network to which it belongs. An IP Address is expressed as four numbers separated by dots (e.g. See also Domain Name.
A global network linking millions of computers for communications purposes. The Internet was developed in 1969 for the U.S. military and gradually grew to include educational and research institutions. In recent years, use of the Internet has mushroomed, primarily due to the popularity of the World Wide Web and electronic mail.
A range of consecutive IP addresses (also known as a subnet), usually belonging to the same organisation.
Netcraft is an Internet services company based in Bath, England. Netcraft is funded through retained profit and derives its revenue in the following ways:
  • Providing network security services, including application testing and automated penetration testing.
  • Providing research data and analysis on many aspects of the Internet. Netcraft has explored the Internet since 1995 and is a respected authority on the market share of web servers, operating systems, hosting providers, ISPs, encrypted transactions, electronic commerce, scripting languages and content technologies on the Internet.
For more information, please see the FAQ section titled "Who are Netcraft?".
Netcraft Web Server Survey
The Netcraft Web Server Survey is a survey of every server on the World Wide Web. As of July 2004, this survey contained 51,642,437 sites.
New Site

"New Site" in the Netcraft Google Chrome™ Extension (Firefox version similar)

"New Site" means the site you are currently visiting has not been seen before by the Netcraft Web Server Survey. This indicates that the site is very new and should be considered less trustworthy than other sites. Since most phishing sites spring up overnight and disappear just as quickly, you should be extremely suspicious if you see this when visiting what you believe to be a trustworthy site.
Phishing is a name derived from the notion of "fishing for information", and "phreaking", which was an eighties term used for people who hacked phone networks and systems to gain access to free calls, or control over parts of the telephony system. It is a simple concept, which is to try to trick people into disclosing their bank account details, so that the attacker may then log in to the person's Internet bank and withdraw their savings.

For more information, please see the FAQ section titled "What is phishing?".

The popularity of a particular web site amongst users of the Netcraft Extension.
Reverse DNS
While DNS is a system of mapping Domain Names to IP addresses, Reverse DNS provides the reverse of this: mapping IP addresses to Domain Names. Since many Domain Names can point to the same IP address, you may not get the same result from the Reverse DNS of a DNS lookup.
Risk Rating
The Netcraft Extension displays a risk rating for each site it encounters. These can be calculated on the fly for sites that Netcraft has never encountered before. Several factors are used to calculate the risk rating, including site longevity, hosting location and historical trends.
SSL (Secure Socket Layer)
Secured Sockets Layer is a protocol that transmits your communications over the Internet in an encrypted form. SSL ensures that the information is sent, unchanged, only to the server you intended to send it to. Online banking sites always use SSL technology to safeguard your personal information.
Site Report
A report detailing aspects of a web site not normally available without specialist knowledge, such as the organisation responsible for the site. This report is designed to provide you with the information you need to make an informed decision about the sites you visit.
URL (Uniform Resource Locator)
The standard way to give the address of any resource on the Internet that is part of the World Wide Web (WWW), e.g. See also: World Wide Web.
WWW (World Wide Web)
The collection of pages which are accessed via the Internet using a browser. Often mistakenly used to refer to the Internet as a whole.