According to an address to the community, Riot has dealt with more Distributed Denial of Service (DDOS) attacks in the past two months, than it has in the previous four years. They've grown exponentially in size too, to the point where when some of them are launched, they don't even reach Riot's servers, they take down their ISP.
This makes it very hard for Riot to implement any sort of fix as the problem is no longer theirs, but everyone's. Players then get severe lag or are disconnected and then you have tens of thousands of people trying to log back in, further stressing login servers and creating nasty queue wait times.
There is light at the end of the tunnel though: "We expect the current attacks to get better soon," said Riot's VP of network operations, sonicdeathmonk.
However, Riot acknowledges that there will be no single solution to fix this issue. It's an "arms race," where as soon as one fix is put in place, another hole will be made by the hackers, but all Riot can do is keep fighting the good fight, so you can fight yours in the Summoner's Rift.