Rainbow Six: Siege players are complaining that the game continues to make their global IP address available to other players, putting those players at risk for DDoS attacks from bitter opponents.
The problem seems to stem from the way the game implements voice chat between players. Back in September, Ubisoft confirmed that while the game uses dedicated servers to host matches, it still uses direct, peer-to-peer connections "strictly to support voice and chat comms for a team." Beta players began noticing almost immediately that this infrastructure decision presents a pretty big security hole when playing with strangers on the Internet. This netcode analysis from January shows how a simple packet sniffer like NetLimiter could easily reveal the IP addresses of all other players in the match, even though voice chat is only available between teammates during a match.
Armed with these IP addresses, unscrupulous players could easily use any number of services to initiate a DDoS attack to remove opposing players from the game. There's a decent amount of evidence that many players were doing just that to gain a leg up in ranked matches, with some managing to climb the in-game ranking ladder despite awful play statistics.