Web Search Engine

A web search engine is designed to search for information on the World Wide Web and FTP servers. The search results are generally presented in a list of results and are often called hits. The information may consist of web pages, images, information and other types of files. Some search engines also mine data available in databases or open directories. Unlike web directories, which are maintained by human editors, search engines operate algorithmically or are a mixture of algorithmic and human input.

How Search Engines Work

The term "search engine" is often used generically to describe both crawler-based search engines and human-powered directories. These two types of search engines gather their listings in radically different ways.
Crawler-Based Search Engines
Crawler-based search engines, such as Google, create their listings automatically. They "crawl" or "spider" the web, then people search through what they have found.
If you change your web pages, crawler-based search engines eventually find these changes, and that can affect how you are listed. Page titles, body copy and other elements all play a role.
Human-Powered Directories
A human-powered directory, such as the Open Directory, depends on humans for its listings. You submit a short description to the directory for your entire site, or editors write one for sites they review. A search looks for matches only in the descriptions submitted.
Changing your web pages has no effect on your listing. Things that are useful for improving a listing with a search engine have nothing to do with improving a listing in a directory. The only exception is that a good site, with good content, might be more likely to get reviewed for free than a poor site.
"Hybrid Search Engines" Or Mixed Results
In the web's early days, it used to be that a search engine either presented crawler-based results or human-powered listings. Today, it extremely common for both types of results to be presented. Usually, a hybrid search engine will favor one type of listings over another. For example, MSN Search is more likely to present human-powered listings from LookSmart. However, it does also present crawler-based results (as provided by Inktomi), especially for more obscure queries.
Crawler-based search engines have three major elements. First is the spider, also called the crawler. The spider visits a web page, reads it, and then follows links to other pages within the site. This is what it means when someone refers to a site being "spidered" or "crawled." The spider returns to the site on a regular basis, such as every month or two, to look for changes.The Parts Of A Crawler-Based Search Engine
Everything the spider finds goes into the second part of the search engine, the index. The index, sometimes called the catalog, is like a giant book containing a copy of every web page that the spider finds. If a web page changes, then this book is updated with new information.
Sometimes it can take a while for new pages or changes that the spider finds to be added to the index. Thus, a web page may have been "spidered" but not yet "indexed." Until it is indexed -- added to the index -- it is not available to those searching with the search engine.
Search engine software is the third part of a search engine. This is the program that sifts through the millions of pages recorded in the index to find matches to a search and rank them in order of what it believes is most relevant. You can learn more about how search engine software ranks web pages on the aptly-named How Search Engines Rank Web Pages page.

Major Search Engines: The Same, But Different
All crawler-based search engines have the basic parts described above, but there are differences in how these parts are tuned. That is why the same search on different search engines often produces different results. Some of the significant differences between the major crawler-based search engines are summarized on the Search Engine Features Page. Information on this page has been drawn from the help pages of each search engine, along with knowledge gained from articles, reviews, books, independent research, tips from others and additional information received directly from the various search engines.
Now let's look more about how crawler-based search engine rank the listings that they gather.

Types of malware

The more you educate yourself on malicious software, the better off you'll be. Malware is not a virus. In fact, it consists of viruses, worms, Trojan horses, adware, rootkits and many other nasty infections. Some of these programs are more of an annoyance than anything, while others pose a serious threat to your computer. Regardless of the type, each of them offer their own unique security threat, and they should be avoided at all costs.

Viruses

The computer virus is the most infamous form of malware. It is a self replicating program that infects a system without authorization. A virus is often transmitted via email but can also be distributed through various storage mediums such as a flash drive. Once installed, it will execute itself, infect system files, and attempt to propagate to other systems. The impact of a virus ranges widely from slow system performance to wiping out every file on your computer.

Worms

Though closely related, worms and viruses are two completely different types of malware. Both have the ability to self-replicate and propagate by attaching themselves to files. While a virus moves from machine to machine, a worm tends to leach onto network traffic and can be a corporation's worst nightmare. In no time, it can travel through the internet and inflict great damage from deleting files to creating backdoors that give its creator control of a system.

Trojan Horses

Similar to the mythical wooden horse used by the Greeks to invade Troy, the Trojan horse is a very deceptive program that appears harmless but is actually one of the most dangerous types of malware. It may arrive as a friendly email attachment or present itself as a useful application on a website. Because it does not have the ability to self replicate, a Trojan cannot be classified as a virus. However, it does have the ability to deliver destructive payloads and unload viruses, worms or spyware.

Spyware

Spyware is a sneaky program that tracks and reports your computing activity without consent. While it isn't designed to inflict damage, spyware can terribly affect the performance of your computer over time. Spyware usually comes bundled with free software and automatically installs itself with the program you intended to use. Signs of spyware include sudden modifications to your web browser, redirects of your search attempts and the frequent displaying of pop-ups. In this instance, spyware can also be termed as adware which is essentially add-supported software that has the ability to track your activity.

Rootkits

A rookit could be a single program or collection of programs designed to take complete control of a system. This type of malware is employed by hackers and gives them all the abilities of a system administrator from a remote location.

Rootkits are very sophisticated as they make hackers very difficult to find. They are often used to infect other computers and enslave them as zombies, forcing them to attack other machines, distribute spam or steal passwords. When attempting to track a rootkit's creator, the search usually ends with the first zombie while the hacker goes undetected.

Staying Safe

As you can see, malware is abundant and will attempt to attack your from every direction. However, there are several security solutions and system updates that will help to keep you protected. Combine these tools with safe computing and you have a much better chance of keeping the malicious software away.

Video conference problems

1. Eye Contact: Eye contact plays a large role in conversational turn-taking, perceived attention and intent, and other aspects of group communication. While traditional telephone conversations give no eye contact cues, many videoconferencing systems are arguably worse in that they provide an incorrect impression that the remote interlocutor is avoiding eye contact. Some telepresence systems have cameras located in the screens that reduce the amount of parallax observed by the users. This issue is also being addressed through research that generates a synthetic image with eye contact using stereo reconstruction.
2. Appearance Consciousness: A second psychological problem with videoconferencing is being on camera, with the video stream possibly even being recorded. The burden of presenting an acceptable on-screen appearance is not present in audio-only communication. Early studies by Alphonse Chapanis found that the addition of video actually impaired communication, possibly because of the consciousness of being on camera.

3. Signal latency: The information transport of digital signals in many steps need time. In a telecommunicated conversation, an increased latency larger than about 150-300ms becomes noticeable and is soon observed as unnatural and distracting. Therefore, next to a stable large bandwidth, a small total round-trip time is another major technical requirement for the communication channel for interactive videoconferencing.