New Physics constraints by rare decays at the B factories

In this article, we review recent measurements of rare decays at the B factories Belle and BaBar which have a strong sensitivity to physics beyond the Standard Model. In particular, we discuss measurements of B+→τ+ντ, B→D(⁎)τ+ντ, and processes that proceed through b→sγ or b→sℓ+ℓ− at the quark level.