Verification code can effectively prevent hackers from constantly trying to crack the password of a specific registered user with a specific program. In fact, using verification code is a common way adopted by many websites (such as online personal banking of China Merchants Bank and QQ community of Tencent).
The main purpose of verification code is to force human-computer interaction and resist machine automation attacks. Most captcha designers have no concept and do not understand basic concepts such as image processing, machine vision, pattern recognition and artificial intelligence.