It appears that on Thursday, the League of Legends servers had been facing an immense amount of lag and downtime. It seems a reason for the problem was an all-to-familiar pest causing problems.
The same group that was responsible for causing huge chaos at the end of 2013 seems to have come back as the group had taken responsibility for the constant server downtime over the last 12-24 hours. As proof of their claims to be responsible, the group has been restoring and re-attacking the servers at will.
As of now, the North American and European servers continue to drop randomly. Developer Riot Games has said that they’ve been working on the issues while the group still solved while the group continues to taunt the team and its fans.
Source: Michael Straw