Modern security-aware embedded systems need protection against fault attacks. These attacks rely on intentionally induced faults. Such intentional faults have not only a different origin, but also a different nature than errors that fault-tolerant systems usually have to face. For instance an adversary who attacks the circuit with two lasers can potentially induce two errors at different positions. Such errors can not only defeat simple double modular redundancy schemes, but as the authors show, also naive schemes based on any linear code over GF(2). In this paper, they describe arithmetic logic units (ALUs) which provide high error detection rates even in the presence of such errors.