WHAT IS CAPTCHA ?

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. 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 to game 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.

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Cool Note Pad Tricks

Notepad Trick

Make a Personal Diary(Log) with Notepad (Easter Eggs)

Notepad Diary

You can use this trick to create a personal log with Notepad which will automatically include the current date and time before your note. To do so, open Notepad and type .LOG in capital letters and press Enter. Save the file. Now, every time you open this file, notepad will automatically insert the current time and date before the note. Just enter your note and save the file each time after making an entry.

All these Notepad tricks are totally harmless and would not harm your PC in any way.  To close any of the VBS trick given, open task manager and close the wscript.exe process. These tricks work on Windows 8, Windows 7, Windows Vista and Windows XP.

Matrix Falling Code Effect - Notepad CMD (.BAT) Tricks

Inspired by the movie Matrix, this falling code trick is extremely popular on social networking websites. Copy and paste the code given below in Notepad and save the file as "Matrix.bat" or *.bat. 

@echo off
color 02
:tricks
echo %random%%random%%random%%random%%random%%random%%random%%random%
goto tricks

Matrix Falling Code Effect - Notepad Trick

Upon running the bat file, you will see the "Matrix falling code" effect.

Create a Harmless Funny Virus with Notepad-Continuously eject CD/DVD drives

This VBS trick will create a code which will continuously eject all your connected Optical drives. If you put them back in, it will pop them out again. Copy this code and paste it in Notepad as Virus.vbs or *.vbs.

Set oWMP = CreateObject("WMPlayer.OCX.7")
Set colCDROMs = oWMP.cdromCollection
do
if colCDROMs.Count >= 1 then
For i = 0 to colCDROMs.Count - 1
colCDROMs.Item(i).Eject
Next
For i = 0 to colCDROMs.Count - 1
colCDROMs.Item(i).Eject
Next
End If
wscript.sleep 5000
loop

Double click to open this file and you will be impressed by this awesome trick.

Make Your Keyboard Type (Any) Message Continuously-VBS Trick

This VBS trick can make any of your friend's keyboard type any message continuously. Open Notepad, copy the code given below and save the file as Tricks.vbs or *.vbs. You will need to restart your computer to stop this. Try this after closing all important programs.

Set wshShell = wscript.CreateObject("WScript.Shell")
do
wscript.sleep 100
wshshell.sendkeys "This is a Virus. You have been infected."
loop

Send this file to your friends as an email attachment to see the fun.

Notepad Trick to Shutdown Computer Forcefully

Open Notepad.

Paste the following code in it:

@echo off

msg * Shutdown computer.

shutdown -c “Sleep Tight” -sn Notepad.

6.Format Hard Disk with Notepad (try it on your enemies)

Picture

Write The Following In Notepad Exactly as it says

Code : 01001011000111110010010101010101010000011111100000

Save As it as .EXE and any Name would Do.

Make an Ethical use of it. This .exe file can be really dangerous.