A denial-of-service (DoS) is an attack that attempts to disrupt the normal function of traffic on a network or server. When successful, it leads to traffic congestion and the inability to reach servers or services. A Sybil attack is characterized by an attacker using spam on a network with nodes so that it can subvert a network's reputation system.
With this release, we have disabled the IP-based parts of the Sybil attack detection tool which were targeted to amplify the effect and duration of the attack. This should help the network return to normal operation.