“World of Warcraft: Warlords of Draenor” reached the PC and Mac on Thursday. Within less than 24 hours,  the popular expansion pack was hit by a major DDoS attack, which is a human or bot-generated attempt to make a machine or network resource unavailable to users.

Irvine, California-based Blizzard Entertainment was already having issues with the game due to the massive amount of players attempting to log in and experience the expansion pack for the first time. This led to a delay in game accessibility and frustration amongst eager users. However, the most serious threat “Warlords of Draenor” faced was a confirmed DDoS attack in North America.

“Our top priority continues to be service issues impacting performance and long wait times on North American realms,” Blizzard said in a forum post on Thursday night. “If you experience issues logging in, please be patient and wait a few minutes before trying again.”

The attacks most likely originated in China, and Blizzard swiftly responded by rolling out updates, some causing a number of other issues within “Warlords of Draenor.” Besides the attack, Blizzard told users its largest issue was the concentration of “players in specific areas and zones.” The developer has been working on maintenance issues since 5 a.m. PST on Friday, anticipating that the process will last around four hours.

“Warlords of Draenor” is the fifth expansion pack for the well-known “World of Warcraft” massively multiplayer online game, allowing players to increase their existing level cap from 90 to 100. The expansion takes place after 2012’s “Mists of Pandaria” and is set in the world of Draenor. Currently, “World of Warcraft” has 7.4 million users.