In this paper we show two attacks against universally resilient mix-nets. The first attack can be used against a number of mixnets, including Furukawa-Sako01 [6], Millimix [11], Abe98 [1], MiP-1, MiP-2 [2, 3] and Neff01 [19]. We give the details of the attack in the case of Furukawa-Sako01 mix-net. The second attack breaks the correctness of Millimix [11] . We show how to counter these attacks, and give efficiency and security analysis for the proposed countermeasures.