But have you ever wondered how CAPTCHA work, and why websites force you to solve them?
What Is CAPTCHA?
CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. As the name suggests, it distinguishes between humans and computers.
The basic concept of CAPTCHA relies on the lack of computer intelligence to recognize patterns. A computer can recognize letters but not in cases where they are altered or present with a lot of background noise. Humans, meanwhile, are hard-wired for generations to spot and identify patterns as a safety mechanism.
Types of CAPTCHA
CAPTCHA comes in various types, a few of them are:
1. Text-Based Image CAPTCHA
Text-based CAPTCHA uses a set of words or phrases or a random combination of different letters, numbers, and symbols. It represents a sequence of characters in an alienated form that’s a little difficult to interpret.
These include distortion, rotation, flipping, wobbliness, capitalization style, and overlapping with adjoining characters. To enhance this technique, a CAPTCHA may include graphics such as lines, arcs, or dots in a randomized fashion, spread throughout the image.
2. Audio CAPTCHA
Audio CAPTCHA serves as an alternative to text-based CAPTCHAs and caters to visually impaired users. Audio CAPTCHA presents an audio recording of a sequence of letters or numbers that the user has to enter correctly. Again, there is distortion, this time in the form of added background noise. An interesting thing to note is that the Python CAPTCHA module only works with numbers.
3. Image CAPTCHA
Image CAPTCHAs are an alternative to text-based image CAPTCHAs. These are the typical CAPTCHAs you will tackle daily.
These CAPTCHAs ask you to identify a particular object such as a boat, truck, or fire hydrant. They present these alongside other images to pick from. These are much more human-friendly than text-based tests as well as more difficult for bots to recognize.
4. Math, Word Problem, and Puzzle CAPTCHA
Math CAPTCHAs often represent a simple arithmetic problem such as 17 + 23, 16 * 10, or 30 / 10 with added graphic elements.
Word Problem CAPTCHA presents a sequence of words or related items and asks you to fill in the blanks with the appropriate response.
Puzzle CAPTCHA involves solving a mini jigsaw puzzle such as sliding a bar to the correct length so that the missing piece completes the image.
5. No CAPTCHA ReCAPTCHA
Google owns ReCAPTCHA which uses advanced risk analysis and adaptive challenges to prevent bots. ReCAPTCHA retrieves content from Google Street View, newspapers, books, and more.
No CAPTCHA ReCAPTCHA requires you to check the “I’m not a robot” option without asking you to go through any tests. This is possible as it tracks the movements and identifies the click. One thing to note is that ReCAPTCHA captures your private information as well.
You can create a CAPTCHA validation form using HTML, CSS, and JS as well as using the Python CAPTCHA module.
The Python CAPTCHA Module
Python comes with a fantastic module called CAPTCHA that helps you create text-based image and audio CAPTCHAs in moments. Though the module provides an inbuilt font style and voice, you can use your voice and font data to customize CAPTCHAs even further.
To install the CAPTCHA module in your Python environment, open the Terminal window and type:
How to Generate a Text-Based Image CAPTCHA Using Python
You can follow these steps to create a text-based image CAPTCHA using Python:
Import the ImageCaptcha module situated in captcha. image.
importing the required librariesfrom captcha.
image import ImageCaptcha Specify a custom width and height for your CAPTCHA and create an instance of it.
specify dimensionsimage = ImageCaptcha(width = 300, height = 100) Take a sequence of characters as user input using the input() function to convert it into a text-based CAPTCHA format.
enter the text to create its captchacaptcha_text = input(“Please enter text: “) Pass the text you got from the user to the image.
generate() to create the CAPTCHA.
generate the text-based captchadata = image.
generate(captcha_text) Pass the text of the CAPTCHA and the image file name along with its extension to image. write() to save the generated image CAPTCHA.
save the captcha image fileimage.
write(captcha_text, (captcha_text) + “. png”)
Output of Text-Based Image CAPTCHA Using Python
One of the best features of this module is that it generates the same text in different colors, styles, and skewness. These are a few of the generated examples.
This is yet another fascinating design generated via the same program.
How to Generate an Audio CAPTCHA Using Python
Follow these steps to create an audio CAPTCHA using Python:
Import the AudioCaptcha module from captcha. audio.
importing the required librariesfrom captcha.
audio import AudioCaptcha Create an instance of AudioCaptcha().
creating an audio instanceaudio = AudioCaptcha() Take digits as user input using the input() function to create its audio CAPTCHA.
audio captcha number, eg: 32135captcha_text = input(“Please enter number: “) Pass the text you got from the user to audio.
generate() to create the CAPTCHA.
generate the audio-based captchaaudio_data = audio.
generate(captcha_text) Pass the text of the CAPTCHA and the audio file name along with its extension to audio. write() to save the generated audio CAPTCHA.
save the audio fileaudio.
write(captcha_text, “audio”+captcha_text+’. wav')
If you enter the numbers 970322, this audio CAPTCHA program will generate an audio970322.wav file that speaks the digits in sequence with a bunch of background noise.
The Many Uses of CAPTCHA
A CAPTCHA’s primary function is to prevent spam and abuse by bots on a website. They help maintain the accuracy of online polls by preventing bots from flooding them with negative responses. They act as a layer of protection against brute force attacks and restrict the number of times a user tries to log in to a website.
CAPTCHA can also help prevent automated comments and can help secure payment gateways with their difficulty to solve.
