Active learning-based fraud detection techniques are provided in adaptive authentication systems. An authentication request from an authentication requestor is processed by receiving the authentication request from the authentication requester; comparing current data for the user associated with the user identifier with historical data for the user; generating an adaptive authentication result based on the comparison indicating a likelihood current user data is associated with a fraudulent user; and performing one or more additional authentication operations to improve learning if the request satisfies one or more predefined non-risk based criteria. The predefined non-risk based criteria comprises, for example, (i) the request receiving a riskiness score below a threshold based on current data and wherein the request was expected to have a risk score above a threshold, or (ii) the request being in a bucket having a number of tagged events below a threshold.