  Face recognition systems are widely deployed for biometric authentication.
Despite this, it is well-known that, without any safeguards, face recognition
systems are highly vulnerable to presentation attacks. In response to this
security issue, several promising methods for detecting presentation attacks
have been proposed which show high performance on existing benchmarks. However,
an ongoing challenge is the generalization of presentation attack detection
methods to unseen and new attack types. To this end, we propose a new T-shirt
Face Presentation Attack (TFPA) database of 1,608 T-shirt attacks using 100
unique presentation attack instruments. In an extensive evaluation, we show
that this type of attack can compromise the security of face recognition
systems and that some state-of-the-art attack detection mechanisms trained on
popular benchmarks fail to robustly generalize to the new attacks. Further, we
propose three new methods for detecting T-shirt attack images, one which relies
on the statistical differences between depth maps of bona fide images and
T-shirt attacks, an anomaly detection approach trained on features only
extracted from bona fide RGB images, and a fusion approach which achieves
competitive detection performance.
