Sunday, August 5, 2007


HijackThis, sometimes abbreviated HJT, is freeware spyware-removal tool for Microsoft Windows originally created by Merijn Bellekom, and later sold to Trend Micro. The program is notable for taking a heuristic approach on detecting malware - rather than relying on a database of known spyware it quickly scans a user's computer, creates a list of differences from a known spyware-free environment and allows the user to decide what from the list needs to be removed.

Google Earth

Google Earth is a virtual globe program that was originally called Earth Viewer and was created by Keyhole, Inc. It maps the earth by the superimposition of images obtained from satellite imagery, aerial photography and GIS 3D globe. It is available under three different licenses: Google Earth, a free version with limited functionality; Google Earth Plus ($20), which includes a few more features; and Google Earth Pro ($400 p.a.), intended for commercial use.

Formerly known as Earth Viewer, Google Earth was developed by Keyhole, Inc., a company acquired by Google in 2004. The product was renamed Google Earth in 2005 and is currently available for use on personal computers running Microsoft Windows 2000, XP, or Vista; Mac OS X 10.3.9 and above; Linux (released on June 12, 2006); and FreeBSD. In addition to releasing an updated Keyhole based client, Google also added the imagery from the Earth database to their web based mapping software. The release of Google Earth caused a more than tenfold increase in media coverage on virtual globes between 2005 and 2006, driving public interest in geospatial technologies and applications.
Denver, Colorado, viewed in Google Earth, now almost completely modeled with high-quality 3D models.
Denver, Colorado, viewed in Google Earth, now almost completely modeled with high-quality 3D models.

The viewer will show houses, the color of cars, and even the shadows of people and street signs. The degree of resolution available is based somewhat on the points of interest, but most land (except for some islands) is covered in at least 15 meters of resolution. Las Vegas, Nevada and Cambridge, Massachusetts include examples of the highest resolution, at 15 cm (6 inches). Google Earth allows users to search for addresses (for some countries only), enter coordinates, or simply use the mouse to browse to a location.

Google Earth also has digital elevation model (DEM) data collected by NASA's Shuttle Radar Topography Mission. This means one can view the Grand Canyon or Mount Everest in three dimensions, instead of 2D like other map programs/sites. Since 23 November 2006, the 3D views of many mountains, including Mount Everest, have been improved by the use of supplementary DEM data to fill the gaps in SRTM coverage. In addition, Google has provided a layer allowing one to see 3D buildings for many major cities in the US and Japan.

Many people using the applications are adding their own data and making them available through various sources, such as the BBS or blogs mentioned in the link section below. Google Earth is able to show all kinds of images overlaid on the surface of the earth and is also Web Map Service client.

Google Earth supports managing three-dimensional geospatial data through Keyhole Markup Language (KML). It is available in a free version, and in licensed versions for commercial use.
Downtown Los Angeles, using the 3D Warehouse feature.
Downtown Los Angeles, using the 3D Warehouse feature.

Google Earth has the capability to show 3D buildings and structures (such as bridges), which consist of users' submissions using SketchUp, a 3D modeling program. In prior versions of Google Earth (before Version 4), 3D buildings were limited to a few cities, and had poorer rendering with no textures.

Many buildings and structures from around the world now have detailed 3D structures; including (but not limited to): U.S., Canada, India, Japan, United Kingdom, Germany, Pakistan, Amsterdam and Alexandria. Three-dimen

Saturday, July 21, 2007

Voice telephony (VoIP)

VoIP stands for Voice over IP, where IP refers to the Internet Protocol that underlies all Internet communication. This phenomenon began as an optional two-way voice extension to some of the Instant Messaging systems that took off around the year 2000. In recent years many VoIP systems have become as easy to use and as convenient as a normal telephone. The benefit is that, as the Internet carries the actual voice traffic, VoIP can be free or cost much less than a normal telephone call, especially over long distances and especially for those with always-on ADSL or DSL Internet connections.
Thus VoIP is maturing into a viable alternative to traditional telephones. Interoperability between different providers has improved and the ability to call or receive a call from a traditional telephone is available. Simple inexpensive VoIP modems are now available that eliminate the need for a PC.
Voice quality can still vary from call to call but is often equal to and can even exceed that of traditional calls.
Remaining problems for VoIP include emergency telephone number dialing and reliability. Currently a few VoIP providers provide some 911 dialing but it is not universally available. Traditional phones are line powered and operate during a power failure, VoIP does not do so without a backup power source for the electronics.
Most VoIP providers offer unlimited national calling but the direction in VoIP is clearly toward global coverage with unlimited minutes for a low monthly fee.
VoIP has also become increasingly popular within the gaming world, as a form of communication between players. Popular gaming VoIP clients include Ventrilo and Teamspeak, and there are others available also.


The concept of sending electronic text messages between parties in a way analogous to mailing letters or memos predates the creation of the Internet. Even today it can be important to distinguish between Internet and internal e-mail systems. Internet e-mail may travel and be stored unencrypted on many other networks and machines out of both the sender's and the recipient's control. During this time it is quite possible for the content to be read and even tampered with by third parties, if anyone considers it important enough. Purely internal or intranet mail systems, where the information never leaves the corporate or organization's network, are much more secure, although in any organization there will be IT and other personnel whose job may involve monitoring, and occasionally accessing, the email of other employees not addressed to them. Web-based email (webmail) between parties on the same webmail system may not actually 'go' anywhere—it merely sits on the one server and is tagged in various ways so as to appear in one person's 'sent items' list and in others' 'in boxes' or other 'folders' when viewed.

The World Wide Web

Many people use the terms Internet and World Wide Web (a.k.a. the Web) interchangeably, but in fact the two terms are not synonymous. The Internet and the Web are two separate but related things. The Internet is a massive network of networks, a networking infrastructure. It connects millions of computers together globally, forming a network in which any computer can communicate with any other computer as long as they are both connected to the Internet. Information that travels over the Internet does so via a variety of languages known as protocols.
The World Wide Web, or simply Web, is a way of accessing information over the medium of the Internet. It is an information-sharing model that is built on top of the Internet. The Web uses the HTTP protocol, only one of the languages spoken over the Internet, to transmit data. Web services, which use HTTP to allow applications to communicate in order to exchange business logic, use the Web to share information. The Web also utilizes browsers, such as Internet Explorer or Netscape, to access Web documents called Web pages that are linked to each other via hyperlinks. Web documents also contain graphics, sounds, text and video.
The Web is just one of the ways that information can be disseminated over the Internet. The Internet, not the Web, is also used for e-mail, which relies on SMTP, Usenet news groups, instant messaging, file sharing (text, image, video, mp3 etc.) and FTP. So the Web is just a portion of the Internet, albeit a large portion, but the two terms are not synonymous and should not be confused.
Through keyword-driven Internet research using search engines, like Google, millions worldwide have easy, instant access to a vast and diverse amount of online information. Compared to encyclopedias and traditional libraries, the World Wide Web has enabled a sudden and extreme decentralization of information and data.
Many individuals and some companies and groups have adopted the use of "Web logs" or blogs, which are largely used as easily-updatable online diaries. Some commercial organizations encourage staff to fill them with advice on their areas of specialization in the hope that visitors will be impressed by the expert knowledge and free information, and be attracted to the corporation as a result. One example of this practice is Microsoft, whose product developers publish their personal blogs in order to pique the public's interest in their work.
For more information on the distinction between the World Wide Web and the Internet itself—as in everyday use the two are sometimes confused—see Dark internet where this is discussed in more detail.


The Internet Corporation for Assigned Names and Numbers (ICANN) is the authority that coordinates the assignment of unique identifiers on the Internet, including domain names, Internet Protocol (IP) addresses, and protocol port and parameter numbers. A globally unified namespace (i.e., a system of names in which there is one and only one holder of each name) is essential for the Internet to function. ICANN is headquartered in Marina del Rey, California, but is overseen by an international board of directors drawn from across the Internet technical, business, academic, and non-commercial communities. The US government continues to have the primary role in approving changes to the root zone file that lies at the heart of the domain name system. Because the Internet is a distributed network comprising many voluntarily interconnected networks, the Internet, as such, has no governing body. ICANN's role in coordinating the assignment of unique identifiers distinguishes it as perhaps the only central coordinating body on the global Internet, but the scope of its authority extends only to the Internet's systems of domain names, IP addresses, and protocol port and parameter numbers.
On November 16, 2005, the World Summit on the Information Society, held in Tunis, established the Internet Governance Forum (IGF) to discuss Internet-related issues.

Router Function

A more precise definition of a router is a computer networking device that interconnects separate logical subnets. Routers are now available in many types, though all are fundamentally doing the same job. A router is a computer whose software and hardware are usually tailored to the tasks of routing and forwarding, generally containing a specialized operating system (e.g. Cisco's IOS), RAM, NVRAM, flash memory, and a small processor. However, with the proper software (such as XORP or Quagga), even commodity PCs can act as routers.
Routers connect to two or more logical subnets, which do not necessarily map one-to-one to the physical interfaces of the router.[2]
The term switch or layer 3 switch or network switch often is used interchangably with router, but switch is really a marketing term without a rigorous technical definition (though a switch is commonly understood as a network hub with switched ports, which might or might not also perform additional routing functions).