Visit the mAadhaar mobile app, or the my Aadhaar portal. You can login using your Aadhaar number, captcha and OTP. Next, select whether you want to lock or unlock your biometric data. Once you select lock, your iris, facial recognition and fingerprint data will be locked. During this time, if anyone tried to undertake biometric identification of the Aadhaar holder, they will receive a specific error code 330.