  We propose a novel robust aggregation rule for distributed synchronous
Stochastic Gradient Descent~(SGD) under a general Byzantine failure model. The
attackers can arbitrarily manipulate the data transferred between the servers
and the workers in the parameter server~(PS) architecture. We prove the
Byzantine resilience of the proposed aggregation rules. Empirical analysis
shows that the proposed techniques outperform current approaches for realistic
use cases and Byzantine attack scenarios.
