Improve CAPTCHA's Security Using Gaussian Blur Filter
This addresses security concerns for website administrators by making CAPTCHAs more resistant to automated attacks, though it is an incremental improvement.
The paper tackled the problem of automated registrations on websites by applying a Gaussian Blur filter to visual CAPTCHAs, resulting in CAPTCHAs that are almost unreadable by OCR programs while maintaining high readability for human users.
Providing security for webservers against unwanted and automated registrations has become a big concern. To prevent these kinds of false registrations many websites use CAPTCHAs. Among all kinds of CAPTCHAs OCR-Based or visual CAPTCHAs are very common. Actually visual CAPTCHA is an image containing a sequence of characters. So far most of visual CAPTCHAs, in order to resist against OCR programs, use some common implementations such as wrapping the characters, random placement and rotations of characters, etc. In this paper we applied Gaussian Blur filter, which is an image transformation, to visual CAPTCHAs to reduce their readability by OCR programs. We concluded that this technique made CAPTCHAs almost unreadable for OCR programs but, their readability by human users still remained high.