Why do I need to enter a verification code when I log in? What a hassle

Captcha is generally to prevent batch registration, and it looks difficult to the human eye, let alone a machine. Two like the post bar is not logged in to post to enter the verification code is probably to prevent the occurrence of large-scale anonymous replies At present, many ** in order to prevent users from using robots to automatically register, log in, and irrigate, all use verification code technology. The so-called verification code is to generate a string of randomly generated numbers or symbols, add some interfering pixels (to prevent OCR), and the user will recognize the verification code information by the naked eye, enter the form to submit** verification, and only after the verification is successful can a certain function be used.

2）.Generally, the place where the user ID is registered and the major forums require a verification code.

3）.Common captchas.

1. Four-digit number, a random one-digit string, the most original verification code, the verification effect is almost zero. 2. CSDN** user login is in GIF format, which is currently commonly used as a random number ** verification code. **The characters on the ** are more decent, and the verification effect is better than the previous one.

For those who do not have basic graphic iconography knowledge, it is unbreakable! It's a pity that the program that reads it, on the first day that csdn used it, seems to have been published in the forum, which is really pitiful!

3,QQ**User login is in png format,**Random numbers + random capital English letters,The whole composition is a bit flamboyant,Every time you refresh it,Each character will change its position! Sometimes the ** that comes out can't be recognized by the human eye, it's amazing....4. When MS hotmail is applied, it is in bmp format, random number + random capital English letter + random interference pixel + random position.

5, Google's gmail registration is in jpg format, random English letters + random color + random position + random length. 6. Other major forums are in XBM format, and the content is random.

4) Significance: In order to prevent users from using robots to automatically register, log in, and irrigate, they have adopted captcha technology. The so-called verification code is to generate a string of randomly generated numbers or symbols, add some interfering pixels (to prevent OCR), and the user will recognize the verification code information by the naked eye, enter the form to submit** verification, and only after the verification is successful can a certain function be used.

The function of the verification code: to effectively prevent this problem on a specific registered user with a specific program brute-force cracking method to make continuous login attempts, in fact, the use of verification code is now a lot of popular methods (such as China Merchants Bank's online personal banking, Tencent's QQ community), we use a relatively simple way to achieve this function. Although it is a little more troublesome to log in, this feature is still necessary and important for the community.

However, we still remind everyone to protect their passwords, try to use more than 6 digits of passwords that are mixed with numbers, letters, and symbols, and do not use simple passwords such as 1234 or passwords that are the same or similar to your username. Don't set a password at will just because you just come to iclub to ask questions, and protecting your own password is also protecting yourself, so as not to cause unnecessary trouble to yourself if you are stolen by others.

This is the one who knows the friends inside.

For security purposes, prevent the program from constantly logging in with different passwords to crack it.