An examination of the interactive video CAPTCHA method to resist relay attack

Abstract

CAPTCHA is a kind of challenge response test, which is used to distinguish human users from malicious computer program such as bots. However, the attack technique called relay attack as a method to avoid the CAPTCHA has been devised. This attack relays the CAPTCHA challenges to remote human-solvers, let them to decode CAPTCHA challenges. We used delay time that is caused by communications needed in relay attack. Our new CAPTCHA uses this delay time between communications to prevent relay attacks. We constructed an experimental environment in which relay attack can be simulated, made a series of experiments in order to evaluate the performance of the proposed method.

An evaluation of the interactive video CAPTCHA method against automated attack

“…In addition, it is also difficult for a bot to identify the target using image processing because it looks very similar to the decoy objects. To evaluate the advantages of our system, we tested its resistance to relay attack [2]. Its ability to resist relay attacks was confirmed by identifying the differences in tracking success time between humans and remote human-solvers based on the assumption that delay time would inevitably result from relaying the test to overseas human operators.…”

“…However, these approaches remain insufficiently resistant to bots. In our previous paper, we proposed an interactive video type CAPTCHA that is strongly resistant to relay attacks [2]. A quantitative evaluation of resistance to automated attacks still has not been carried out.…”

Implementation of CAPTCHA suitable for mobile devices

“…2 CAPTCHA for mobile devices 2.1 Implementation of CAPTCHA based on the previous one Although various CAPTCHAs have been proposed [2,3], there is almost no CAPTCHA specialized for mobile devices. In order to realize such CAPTCHA, we extended our previous CAPTCHA to be more suitable for mobile devices [4]. In our previous CAPTCHA, a user tracks one target object among multiple decoy objects.…”