Warning: Even if the Hypixel websites appear to come back online DO NOT attempt to log into them until Hypixel has confirmed they have regained control over their domains and have stated it is safe to access them.
The hack appears to be against Hypixel's network service provider, affecting all domains owned by Hypixel Studios including the IP address used to connect to the Minecraft server.
The hacker has redirected several of Hypixel's domains to their own network.
Attempting to visit a Hypixel-owned domain shows firstly a fake announcement post that the upcoming Hytale video game has been cancelled, and lists the hacker's crypto address to donate to. It may also show a troll message aimed at Hypixel CEO Simon Collins-Laflamme.
Attempting to connect to the Minecraft server results in a failed authentication message. Existing sessions with the server seem intact, until players attempt to relog. It is not recommended to attempt to join the server.
Hypixel notes that they
do not have any reason to believe player information has been compromised.
The Hypixel website appears to come back online intermittently but the website is currently not secure. Do not attempt to log in to website or connect to the server until an all-clear has been given by Hypixel – these still appear to be the hackers' control even when the website appears normal.
This article will be updated when further correspondence from Hypixel is made.
Update: Hypixel have stated it is now safe to access the Minecraft server.