The statement "'Captcha' equals 'malware'" itself has a logical flaw, because "captcha" is not a piece of software, but rather a feature within software. The actual meaning of this statement is that software with the "captcha" feature is "malicious software."
Please don't get upset; let me explain.
A long time ago (actually, not that long), when you logged into a system, all you needed to do was input your "username," "password," and then press "enter." It didn’t take much effort. Later on, some troublemakers (mostly out of boredom) used programs to repeatedly attempt logins on websites in order to steal others' passwords or overload and even crash the system. To address this crisis, someone invented the "captcha."
The most common "captcha" function requires users to identify numbers and letters on an image, then enter the results into an input box, submitting it along with other information to the system. The numbers and letters on the image are the "captcha." Before executing any other operations, the system first verifies whether the "captcha" entered by the user matches what's on the image. If it doesn’t match, the system immediately returns to the client without performing further operations. Even now, image recognition technology is still far from mature, with very low accuracy in recognizing text from images. Therefore, malicious programs almost cannot pass the "captcha" verification. Even if they occasionally succeed once, it’s nearly impossible for them to continuously pass the "captcha" multiple times. As a result, the possibility of using programs to repeatedly log in and obtain others' passwords is almost zero. Moreover, the system only needs to perform one "captcha" verification to reject malicious logins, greatly reducing the system's load. This achieves two goals at once!
Besides image-based "captchas," there are other forms, but I won’t go into detail here. However, the purpose is the same: to allow humans to recognize it while preventing machines from doing so, thereby preventing attacks from malicious programs.
Since the "captcha" feature is so good, how did it come to be associated with "malware"?
The "captcha" feature is indeed excellent, invincible upon its debut! Software designers quickly enlisted its help to enhance their systems' defensive capabilities. Thus, today, when you log into a system, you not only need to input your "username" and "password," but also the "captcha." Your "username" and "password" are memorized, making them easy to input. However, the "captcha" is random, requiring you to identify it each time. There isn’t a unified standard for the "captcha" feature, and different systems use various methods to increase machine recognition difficulty. Some add colors, some add background patterns, some vary font sizes, and some change angles, etc. While these make it harder for machines to recognize, they also make it more difficult for humans. Sometimes, it’s hard to correctly identify the "captcha" on the first try, such as distinguishing between the number "1" and the letter "l," or between uppercase and lowercase letters. Although some systems offer a "refresh captcha" function to help users choose an easier-to-identify "captcha," this doesn’t fundamentally solve the problem and instead requires users to perform additional operations. The essential issue with the "captcha" feature is: every login requires an extra step of entering the "captcha," and the randomness and difficulty of identifying it make this operation increasingly challenging and painful!
The "captcha" feature forces users to perform operations they dislike and find unnecessary (since it wasn’t required before), leaving no room for choice. It’s quite domineering. Users grit their teeth but feel powerless. Therefore, from the user's perspective, it becomes a malicious feature. When legitimate software incorporates a malicious feature, it turns into "malware."
So, does the lengthy description earlier about the benefits of the "captcha" feature for system security mean it was all a lie?
Of course not. The original intention behind the "captcha" feature is good, and its essence is good too. The problem lies in how it is presented to users. It’s like "advertising" — it isn’t inherently malicious, but when it appears in a "forced pop-up" form, it becomes malicious.