Why do you need a verification code if you have a password?

Mainly to prevent OCR.

What the captcha does:

1）.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.

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.

Significance: In order to prevent users from using robots to automatically register, log in, and irrigate, many ** 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.

Prevent hackers. We fill in the password and send it to the network. Hackers can intercept this message halfway through. But the captcha is there and he can't see it, and it can't be displayed.

The verification code is a temporary password, and you can use it to increase security.

This is to ensure accountability to customers or salespeople.

The reason for verifying the correct password is to effectively prevent this kind of problem: to continuously log in to a specific registered user by brute-force attack method with a specific programIn fact, using the verification code is now a lot of ** common way, and we use a relatively simple way to achieve this function. Although it is a little troublesome to log in, this feature is still necessary and important for the community.

A password is a technique used to obfuscate users who want to turn normal (identifiable) information into unrecognizable information. But this unrecognizable part of the information can be reprocessed and restored. The "password" you enter when logging in**, your email address, and withdrawing money from your bank should technically be just a password.

Related information

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 usernames.

The same and similar password, so that you don't have to be stolen and cause unnecessary trouble to yourself.

Captcha usually consists of some lines and some irregular characters, and the main purpose is to prevent some hackers from digitizing the password. The verification code is randomly generated, and there is a high probability that there will be a verification code that cannot be clearly recognized**, so it should be noted that generally**there will be corresponding prompts, such as "I can't see clearly, change one" and so on.

The strategy of introducing CAPTCHAs is primarily to protect your rights and prevent number thieves from using malware to scan your passwords by logging in. But many people don't understand this. Because I felt the seriousness of this kind of problem, I personally added some Q friends who needed to enter a verification code, and got some problems from it.

Everyone has been discussing why there is this captcha? In the survey, it was found that many Q friends generally have two Qs or more than two Qs, but not all of their QQs need to be entered, but only one. The reasons for this are obvious, and now I will classify these regulations for the following reasons:

1. You may have used some unofficial software to log in to QQ, or you have hung up on **, or logged in to Q in some unsafe places, such as Internet cafes with unsafe factors. 3. The reason for the existence of virus Trojans in your computer, such as sending some virus messages or deceptive messages when you are infected by a virus, are caused by viruses. 4. Sending QQ messages maliciously, being reported by others, and forcibly deleting a large number of friends.

5. At the same time, please do not provide the password during the time period of your login number so that your friends can log in elsewhere to try yours, it may also be caused by network problems, such as using **, the network is unstable, and it will appear. Solution: Please use antivirus software to fully kill your computer in safe mode, it is recommended that you clear the local dust chat history of this number (search for the folder named with the number in the QQ installation directory to delete!).

In between, please uninstall all previous QQ versions, **the latest official QQ version to use. There is also the reported QQ number, please be patient and wait for the passage of the observation time, and when the time passes, the verification code will disappear, but you need to re-operate it like the above. The solution to the requirement to enter a verification code for the existence of a double main number in the user's number Due to the recent discovery that a large number of numbers have a double main number (that is, two people know that the number password is used at different times and places at the same time), it is not easy to be discovered by the original number owner, so we have launched a verification code to attract the attention of the real number owner and reduce the loss of the original owner.

1. Send advertising messages: That is, they may be used by others to send advertisements or scam messages without your knowledge, which will be detected by the system. 2. Remote login:

That is, your number often logs in in one place, and when it is suddenly detected that the landing location has changed, it will add a verification code for security purposes 3, and the number hangs up: Usually the thief will use the help of the user to hang up to steal the user's property and number. Workaround:

1. Change the password immediately after discovering the verification code, and kill the Trojan 2. After you are required to verify the password, it will enter the observation period, and the system will automatically cancel it after 10 to 20 days of normal use; If the password is leaked again during this period, you will continue to be asked to enter a verification code.