What is captcha? How to enter or remove captcha? UnCAPTCHA: using Google services to bypass Google reCAPTCHA How to bypass captcha using sql injection

If you more or less actively use the Internet in your daily work, then you probably know about such an unpleasant thing as captcha. Sometimes it interferes so much with their work that people often simply stop visiting those sites whose owners pay too much attention to it.

What it is?

By the way, what is captcha? Imagine that you have visited some popular file hosting service. To download a file in free mode, you will have to enter a certain set of characters (often meaningless) into a special field, which should be taken from the picture opposite.

The task is complicated by the fact that these symbols are sometimes completely impossible to make out, since they are deliberately made unreadable.

What is it for?

Having understood what a captcha is, it would be nice to talk about its specific purpose. Why is it necessary to fence such a garden, making it difficult to send comments or download files?

Yes, there were times when no one knew about captcha at all. It appeared relatively recently. This happened during the same period when a mass of bots proliferated in the vastness of the Runet, with the help of which enterprising citizens left advertisements in the comments, downloaded files for free and did other outrages.

Of course, on many resources administrators kept order, but in most blogging services the load on them turned out to be such that they simply stopped coping. That's when users learned about captcha! The acquaintance turned out to be quite unpleasant.

To be very precise, the technology itself was originally created in 2000. Initially, it was intended only to determine the “humanity” of your interlocutor on the Internet: then not a single program for captcha (to recognize it, more precisely) was simply created.

What is its disadvantage?

If you carefully read the first part of the article, then you can guess most of the negative factors of using captcha on your own. Firstly, most users act in a state of some kind of impulse. Simply put, when you see some interesting post on LiveJournal, you want to immediately comment on it.

But you are faced with an indigestible captcha, and most of the characters are so illegible that it can take more than one day to solve them. Do you think the user will engage in such a thankless task?

Of course not! He will simply go to another site. Thus, if you are trying to protect your resource from those who like to leave spam in comments, we advise you not to try too hard.

If you get too carried away with captcha, you will quickly lose many active users. No users - no money from advertising. In addition, most normal resources automatically recognize spam in comments, so there is often no point in additional protection.

Almost the same can be said about file sharing sites. Of course, one can understand their creators: by offering everyone to download information of interest for free, they will simply miss out on profits.

But this same situation can be looked at from the exact opposite side: if a site offers you the opportunity to receive a file for free, it will easily gain a huge audience that will quickly recoup all costs by attracting advertisers. By the way, this is exactly how the domestic iFolder works, the creators of which certainly cannot complain about poverty.

So, even from the point of view of making a profit, the idea of ​​captcha itself does not look so attractive.

What to do?

How to remove the captcha, is it really possible to do this? The situation here is quite ambiguous. The fact is that on many sites that use this type of anti-spam protection, not every user can read the captcha the first time, not to mention some applications.

Simple options can be recognized using the small Screenshot Reader utility, which is part of the ABBYY FineReader software package. But it only reads the simplest captcha forms, which any normal user can easily recognize. In addition, the process itself cannot be automated, since for recognition you need to manually select the range of interest to you.

Entering captcha

If you don’t have much choice, you’ll have to do this thankless task manually. What advice can you give? First, try to do it quickly: many sites have a counter that resets the value if you cannot enter it within a couple of minutes.

Additionally, typing errors often occur when JavaScript is disabled in your browser. Don’t forget also about the need for Cookies, as they will help the site “recognize” you, eliminating the need to constantly go through annoying protection.

Finally, pay attention to what is written on home page site. As a rule, a captcha for a website is described in detail in an explanatory note or a separate article. An excellent example is the file-sharing service Rapidshare, which at one time introduced a unique captcha.

Its characters were easily distinguishable, and no blurring or polarization technologies were used to make it difficult for programs to recognize it. What was the secret?

And it consisted in the fact that cats were sitting on those letters and numbers that had to be entered into the appropriate field. How many unpleasant words were said at one time about the creators of such a system! In the end, it was abandoned under pressure from the user community.

We buy the “antidote”

Another option is to contact a normal programmer (or a group, which is even better), so that he can create a utility for recognizing captcha on a specific site. Alas, there are no universal solutions, if only because each resource has unique protection. Some standard solutions are very rare.

Of particular interest in this regard are the developments of the CMS Bitrix company, which distributes truly effective programs that cope with captcha on most popular sites. The developers claim that the effectiveness of their creation is within 95%. Depending on the type of protection, its complexity and the specific site, developing methods for protecting it can cost you a couple of thousand dollars, or even more.

In addition, some resources have such sophisticated protection that it is not easy for a person to decipher it!

Is it possible to make money by entering it?

Beginners often wonder if it is possible to somehow make money by entering security symbols. And this is not surprising, because the Internet is full of advertisements for recruiting groups of people who will receive some money by performing captcha recognition. Is it worth getting involved with this?

In our opinion (perhaps quite subjective), this matter is not worth pursuing. You will waste a huge amount of nerves, effort and traffic. And the payment for such “easy money” is simply amazing: after sitting at the computer all day, hammering in captcha with manic persistence, you will earn a maximum of a couple of dollars. Do you need it? Surely not.

Universal output

If we talk about file hosting services, then if you regularly upload files, the only reliable way out of the situation is to buy a paid account. As a rule, its cost is quite adequate. By purchasing such a subscription, you will be able to download any amount of information quickly and without inconvenience.

How to remove captcha from your blog?

We hope that you have made the right conclusions after reading most of our article. Therefore, let’s look at how to remove captcha entry on the popular Blogger service from the notorious one. It’s not difficult to do this at all, and you will bring a lot of joy to the visitors of your site.

First, go to the “Editor” of your page. In the left column, select “Settings”. It has a “Messages and Comments” section. In the “Use word verification” field, set the value “no”, after which the captcha will not be required when entering messages.

What to do if you can’t enter it correctly?

It happens that the program for entering captcha or the site itself (if you enter the values ​​manually) constantly gives an error. What could be the reason?

First of all, you need to calm down. As a rule, there is a curved arrow on the right side of any captcha. By clicking on it, you will update the character set that you need to enter to access the site. Using it, you can change a completely unreadable set. Unfortunately, unreadable letters are very common. So, sometimes the difference between the letters “Q” and “G” is completely indistinguishable.

Finally, on many sites you can avoid entering security characters if you simply register on it. Try this method too.

That's what captcha is!

CAPTCHA: people versus computers

On some websites, you may have noticed that you cannot continue to perform any actions or place an order until you solve a set of incomprehensible letters and images. After you carefully examine some wavy lines, decipher the written words and enter the correct phrase (words or numbers) into the empty field, you can continue your actions on the site. This process is intended so that the site can verify that in fact you are person browsing the site.

This test is called CAPTCHA(Completely Automated Public Turing Test to Tell Humans and Computers Apart), and it is used everywhere on the Internet. The ticketing website Ticketmaster is a great example of the use of CAPTCHA: without such a test, a “robot” could potentially buy millions of tickets to a concert or event, and then resell them at a higher price.

Of course, being required to figure out an incomprehensibly written combination of letters and numbers every time we want to do something is a little annoying. And this requires additional time. Every time you need to pass a CAPTCHA test, you waste approximately 10 seconds of your life. This is why CAPTCHA has earned a bad reputation among Internet users, despite the fact that it was created precisely to keep us safe.

CAPTCHA prevents cyber criminals

Louis Von Ahn, one of the creators of CAPTCHA, continues to develop this test within the framework of Google, its new developer. This project has been revived in reCAPTCHA, an extension of the Captcha test that takes words from scanned pages of old books (those words are harder for a computer to recognize). While protecting our safety, the project simultaneously helps “ digitize texts, image annotations, and build datasets for machine learning“... now at least these 10 precious seconds are used for something more worthwhile.

It's great that we help digitize books, but when it comes to Internet security, is CAPTCHA effective?

Google CAPTCHA can be bypassed too easily

A trio of researchers from Columbia University (New York) proved how easy it is to bypass some CAPTCHAs. Similar programs make it much more difficult for hackers to use programmed bots to automatically and en masse collect addresses Email, which are then used for spam campaigns. But they are not completely reliable. Such processes can be automated, and as a result, computers will be able to pass reCAPTCHA tests as efficiently as you and I.

Captcha technology (CAPTCHA) is an automated test designed to identify machine users, aka bots.

His goal is to pose a problem that can be easily solved by a human, but difficult for a computer.

But there are also situations when a seemingly useful script becomes too intrusive.

There is an assumption that Google is training the AI ​​of its drones, thanks to users entering captcha with pictures I am not a robot.

How to remove captcha I'm not a robot

The reasons for this behavior may vary, but you can always try to fix everything - we carry out actions as exceptions occur:

• Disconnect and reconnect the active Internet connection. Reboot the router or modem. Therefore, the IP address may change.
• We resort to using a VPN service. The latter are both paid and for free use. They are provided in the form of extensions (add-ons) for browsers and as separately installed software on a computer.
• We look through and installed extensions. For example, the latest version of Yandex.Browser itself disables plugins from unverified sources and periodically checks those already installed for fakes.
• Check if JavaScript is enabled in the web browser: Settings → Show additional settings→ personal data block Content settings → JavaScript section.
• Let's not forget about antivirus programs– perhaps the computer has become a victim of a botnet, hence the dissatisfaction with the CAPTCHA for traffic generated at this address.

Interestingly, hundreds of millions of captchas are entered by Internet users every day. It is no secret that not everyone manages to enter it correctly the first time.

Good day, friends! If you are reading this article, it means that you are also having problems with Google recaptcha, which is used by an increasing number of sites. But many users do not like it, but an increasing number of site users are using it. Why it is so good, its disadvantages and how to pass it, all this can be found in this article.

ReCaptcha was created to protect websites from Internet bots and digitize book texts. Since 2009, owned by Google.

what's good about her

As noted earlier, the advantages of this type of captcha are: protection against spam and digitization of book texts.

why is she bad

Of course, this captcha is not ideal and a correctly written bot can easily bypass such recaptchas.

In addition, many users have problems with recaptcha, which they have to solve several times. Below, I will tell you how I complete captchas faster. The method is certainly simple, but not very effective, but it speeds up the time spent on solving the captcha.

What did I notice?

For example, when solving a captcha with road signs, sometimes there are no road signs, then we immediately click skip. But sometimes captcha with road signs, etc. It happens when they are selected and the confirmation is transferred to another captcha. Why? When solving it, I came across only one option (if there are more, write in the comments), when you click on the picture, the “skip” button is replaced with “next”. If the next button appears, then you will not solve this captcha and you will be transferred to the next captcha

There are several nuances

how to pass it and small features of passing captcha.

1)ReCaptcha view

a) Disappearing pictures (remove all unnecessary)

Such captchas are always passed. Personally, I have never had any problems with this type of captcha.

b) Selecting a picture or part of a picture (I’ll give an example below)

I had problems choosing a picture. But I couldn't understand why. For example, in the picture below, the task says: “select all the squares that contain road signs. If they are not there, click the "skip" button. In fact, there is a road sign P = "parking", but ReCaptcha will not count it, because instead of the "skip" button, the "next" button appears, although the road sign is in the task is present, but perhaps the ReCaptcha developers don’t think so. The opposite situation also happens, but I won’t give an example in the article, I think everything is clear to everyone.

2) If this is a captcha with non-disappearing pictures, then select one square and look at the change in the “skip” button.

a) If the button has changed to the “next” button. You will not pass such a captcha, even if there is a solution.

b) If the button has changed to a “confirm” button, then you will pass this captcha if you pass it correctly.

Sincerely, Mars Magafurov

How many years has Habr existed - for so many years, posts about the next captcha regularly appear on it - be it a picture generation script, a new captcha idea with cats, and the like. The most recent example of a person not quite understanding how a captcha should work (see the text of the post and the latest comments), but at the same time sharing his misconceptions with the community. One gets the feeling that captcha is like this terra incognita for most developers - both for those who simply screw it onto the next form in the hope that it will work out of the box, and for those who come up with captchas like those in which you need to select a picture with a cat from several photos.

The article contains useful information for those who use captcha on their server, instead of trusting a third-party service like reCaptcha.

And for starters - if you think that such a captcha check will work:
if($_POST["captcha"] == $_SESSION["captcha"]) return true; (case example)
then you are deeply mistaken.

Captcha

Two main properties of captcha

Resistance to recognition- a property that protects captcha from being recognized by an algorithm, such as a text recognition system. It guarantees that a person can read the text in a picture, but a computer cannot.
Anti-example: the standard captcha of the phpBB 2.x forums did not have this property - due to the relative ease of recognition, scripts appeared that spammed all the forums, forcing webmasters to change the captcha to a more resistant one.

Guess Resistance- a captcha property that does not allow you to guess its value in a small number of attempts (less than 1000). If the set of possible captcha values ​​is small, it will not be difficult for the program to guess it by selection instead of recognition.
Anti-example: arithmetic captcha like “1+2” (searching numbers from 1 to 20 will soon give a result).
Anti-example: choose from several pictures the one that shows a cat.

Captcha check

Before checking the answer, you need to make sure that it is not empty. Otherwise, an attacker can, without loading the picture or deleting the current session identifier, pass an empty value and pass the captcha, because there will be a comparison of the two empty lines(in PHP, a non-existent value is equal to the empty string).
Anti-example: the code I already mentioned if($_POST["captcha"] == $_SESSION["captcha"]) return true;
Moreover, this code was written by an experienced programmer.

After verification, the saved captcha value must be deleted. If you do not do this, the attacker will be able to use this value again an unlimited number of times. Yes, when the page with the form is updated, the captcha is also updated (either when generating the form or when generating the image), but the script may not load the form again (it should be mentioned that this is not relevant if the site uses one-time csrf tokens for forms).
Anti-example: a hypothetical login form in which it is enough to enter the captcha correctly once, and then select the password using a script, avoiding regenerating the captcha on the server.

Bulletproof captcha

DoS protection. When generating a captcha on your server, you need to understand that this is a convenient vector for conducting DoS attacks(which, unlike DDoS, can be carried out by any schoolchild). For protection, you can limit the number of captcha generation for one ip, by caching captchas, etc.

Protection against recognition. If you choose a captcha, or suddenly plan to write it yourself, it is advisable to understand which captcha is more protected from recognition. There are ready-made universal captcha recognition scripts that work on the OCR principle, and if spammers are interested in your site, there is a risk that they will use/write a script specifically for your captcha. The latter truth applies more to sites at the Yandex or VK level, but it is advisable to provide an option with protection against banal OCR.

Anti-gate protection. Formally speaking, captcha as a Turing test is not obliged to protect you from anti-gates, since in this case it will be recognized by a person. From a practical point of view, this issue is very relevant and it is necessary to defend ourselves somehow.
There is not and cannot be a “gold standard” (because in this case anti-gates will implement its support), so you are free to supplement the captcha with any tricks to make its recognition through the anti-gate impossible. For example:
- non-standard captcha (assembling a puzzle, rotating an image, clicking on an area in a photo, etc.);
- Cyrillic captcha is the simplest solution, but has a number of disadvantages: it is only suitable for projects with a Russian-speaking audience, there are anti-gates that support the Cyrillic alphabet;
- usage virtual keyboard next to the captcha for entering non-standard characters or shapes (may be inconvenient for mobile users);

Usability

To facilitate human recognition: do not use both letters and numbers in the captcha, do not use upper and lowercase letters at the same time, exclude similar characters.

Refusal to use captcha

To some, the information in this topic will seem obvious, but if I had not encountered examples of misunderstanding of these simple principles in life, including among experienced fellow developers, I would not have wasted time writing this text.