Techblu3's Blog

What is CAPTCHA and How it Works?

techblu3 — Mon, 26 Jul 2010 01:56:17 +0000

CAPTCHA or Captcha (pronounced as cap-ch-uh) which stands for “Completely Automated Public Turing test to tell Computers and Humans Apart” is a type of challenge-response test to ensure that the response is only generated by humans and not by a computer. In simple words, CAPTCHA is the word verification test that you will come across the end of a sign-up form while signing up for Gmail or Yahoo account. The following image shows the typical samples of CAPTCHA.

Almost every Internet user will have an experience of CAPTCHA in their daily Internet usage, but only a few are aware of what it is and why they are used. So in this post you will find a detailed information on how CAPTCHA works and why they are used.

What Purpose does CAPTCHA Exactly Serve?

CAPTCPA is mainly used to prevent automated software (bots) from performing actions on behalf of actual humans. For example while signing up for a new email account, you will come across a CAPTCHA at the end of the sign-up form so as to ensure that the form is filled out only by a legitimate human and not by any of the automated software or a computer bot. The main goal of CAPTCHA is to put forth a test which is simple and straight forward for any human to answer but for a computer, it is almost impossible to solve.

What is the Need to Create a Test that Can Tell Computers and Humans Apart?

For many the CAPTCHA may seem to be silly and annoying, but in fact it has the ability to protect systems from malicious attacks where people try togame the system. Attackers can make use of automated softwares to generate a huge quantity of requests thereby causing a high load on the target server which would degrade the quality of service of a given system, whether due to abuse or resource expenditure. This can affect millions of legitimate users and their requests. CAPTCHAs can be deployed to protect systems that are vulnerable to email spam, such as the services from Gmail, Yahoo and Hotmail.

Who Uses CAPTCHA?

CAPTCHAs are mainly used by websites that offer services like online polls and registration forms. For example, Web-based email services like Gmail, Yahoo and Hotmail offer free email accounts for their users. However upon each sign-up process, CAPTCHAs are used to prevent spammers from using a bot to generate hundreds of spam mail accounts.

Designing a CAPTCHA System

CAPTCHAs are designed on the fact that computers lack the ability that human beings have when it comes to processing visual data. It is more easily possible for humans to look at an image and pick out the patterns than a computer. This is because computers lack the real intelligence that humans have by default. CAPTCHAs are implemented by presenting users with an image which contains distorted or randomly stretched characters which only humans should be able to identify. Sometimes characters are striked out or presented with a noisy background to make it even more harder for computers to figure out the patterns.

Most, but not all, CAPTCHAs rely on a visual test. Some Websites implement a totally different CAPTCHA system to tell humans and computers apart. For example, a user is presented with 4 images in which 3 contains picture of animals and one contain a flower. The user is asked to select only those images which contain animals in them. This Turing test can easily be solved by any human, but almost impossible for a computer.

Breaking the CAPTCHA

The challenge in breaking the CAPTCHA lies in real hard task of teaching a computer how to process information in a way similar to how humans think. Algorithms with artificial intelligence (AI) will have to be designed in order to make the computer think like humans when it comes to recognizing the patterns in images. However there is no universal algorithm that could pass through and break any CAPTCHA system and hence each CAPTCHA algorithm must have to be tackled individually. It might not work 100 percent of the time, but it can work often enough to be worthwhile to spammers.

12 Tips to Maintain a Virus Free Computer.

techblu3 — Mon, 26 Jul 2010 01:40:37 +0000

Is your computer infected with virus? Do you often get mysterious error messages? Well this is a common problem faced by almost all the computer users across the globe. There are many viruses and worms out there that could infect your computer. Some are harmless, but, they do have the capacity to do any number of nasty things, up to and including, erasing all data from your computer. However there are ways to keep viruses away from your PC. Here are the 12 tips to maintain a virus free computer.

1. Email is one of the common ways by which your computer can catch a virus. So it is always recommended to stay away from SPAM. Open only those emails that has it’s origin from a trusted source such as those which comes from your contact list. If you are using your own private email host (other than gmail, yahoo, hotmail etc.) then it is highly recommended that you use a good anti-spam software. And finally NEVER click on any links in the emails that comes from untrusted sources.

2. USB thumb/pen drives is another common way by which viruses spread rapidly. So it is always a good habit to perform a virus scan before copying any data onto your computer. NEVER double-click the pen drive to open it. Instead right-click on it and select the option “open”. This is a safe way to open a pen drive.

3. Be careful about using MS Outlook. Outlook is more susceptible to worms than other e-mail programs, unless you have efficient Anti-Virus programs running. Use Pegasus or Thunderbird (by Mozilla), or a web-based program such as Hotmail or Yahoo (In Firefox).

4. As we all know, Internet is the main source of all the malicious programs including viruses, worms, trojans etc. In fact Internet contributes to virus infection by up to 80%. So here are the tips for safe surfing habits so that you can ward off virus infection up to the maximum extent.

• Don’t click on pop-up windows that announce a sudden disaster in your city or announce that you’ve won an hourly prize. They are the ways to mislead Internet users and you should never trust them.

• You can also use a pop-up blocker to automatically block those pop-ups.

5. Most of us use search engines like Google to find what we are looking for. It is quite obvious for a malicious website to get listed in the search results. So to avoid visiting those untrusted malicious websites, you can download and install the AVG LinkScanner which is a freeware. This tool can become very handy and will help you to stay away from malicious websites.

6. Install a good antivirus software and keep it updated. Also perform full system scan periodically. It is highly recommended that you turn on the automatic update feature. This is the most essential task to protect your PC from virues. If PC security is your first option then it is recommended that you go for a shareware antivirus software over the free ones. Most of the antivirus supports the Auto-Protect feature that provides realtime security for your PC. Make sure that this feature is turned on.

7. Install a good Antispyware program, that operates against Internet malware and spyware.

8. Never open any email attachments that come from untrusted sources. If it is a picture, text or sound file (these attachments end in the extensions .txt, .jpeg, .gif, .bmp, .tif, .mp3, .htm, .html, and .avi), you are probably safe, but still do a scan before opening.

9. Do not use disks that other people gave you, even from work. The disk could be infected with a virus. Of course, you can run a virus scan on it first to check it out.

10. Set up your Windows Update to automatically download patches and upgrades. This will allow your computer to automatically download any updates to both the operating system and Internet Explorer. These updates fix security holes in both pieces of software.

11. While you download files from untrusted websites/sources such as torrents, warez etc. make sure that you run a virus scan before executing them.

12. And finally it is recommended not to visit the websites that feature illegal/unwanted stuffs such as cracks, serials, warez etc. since they contribute much in spreading of viruses and other malicious programs.

Make partitions in Windows 7

techblu3 — Wed, 07 Jul 2010 04:17:24 +0000

Right click on my computer
click on manage
a window ‘Computer Management’ will open

Disk Management

right click on partition to Shrink and click on Shrink(500gb c: can be shrinked to 248gb) , it will ask you how much to shrink, enter your preferred size ,press ok

now a new partition will appear, right click on it , now select ‘New Volume’ ,enter preffered size , you can use available size for 1 or more partitions (partitions of 100,150gb recommended).

Download youtube Videos on mobile

techblu3 — Thu, 25 Mar 2010 15:29:44 +0000

you can download videos from websites like youtube.com , metacafe.com , google videos,etc easily from your mobile.

just go to abphone.com/ vuclip.com both of them provides youtube videos in 3gp format with good quality and many other features like part downloading.

Download movies

techblu3 — Fri, 06 Nov 2009 15:09:18 +0000

you can easily find movies and download them to ur pc just copy the following links and paste in the address bar
oneclickmoviez.com
icefilms.info
freehdmovie.net

Download youtube videos

techblu3 — Thu, 05 Nov 2009 19:39:02 +0000

you can download youtube videos on ur pc anywhere anytime without any downloading software using your very own firefox browser

open firefox – > tools -> add-ons – > get add-ons – > search -> write “easy youtube downloader”

install it and restart it will take a few seconds to download n install

or u can download the add-on directly from the link

https://addons.mozilla.org/en-US/firefox/addon/10137

now whenever you will open any video on youtube you will see three options FLV , MP4, 3GP .select the file type and the download starts.

———————————————————————–

if you dont have firefox the check the portable apps post or go to portableapps.com

The Airtel Internet

techblu3 — Wed, 28 Oct 2009 09:17:24 +0000

If u have zero balance(0.01-0.29) and u want to surf free u r in the rite place . just download the folowing

http://uploadthis.co.uk/uploads/Devil786/OperaMini_AirtelLive_North_Jbpseudo.jar

The google search trick

techblu3 — Wed, 28 Oct 2009 09:04:14 +0000

Search and download mp3 for free using google hidden serach

go to google.com and search the the following code:

-inurl:htm -inurl:html intitle:”index of” mp3 “linkin park”

replace linkin park with your favorite artist.

Advanced searches

-inurl:(htm|html|php) intitle:”index of” +”last modified” +”parent directory” +description +size +(wma|mp3) “Nirvana”

replace nirvana with artist name , you can add description and file size to the search

This search string can easily be used to search for ebooks in DOC and PDF format:

-inurl:(htm|html|php) intitle:”index of” +”last modified” +”parent directory” +description +size +(pdf|doc) “george orwell 1984″

Or perhaps you’re looking for some specific video file:

-inurl:(htm|html|php) intitle:”index of” +”last modified” +”parent directory” +description +size +(mpg|wmv) “towelie”

regards.