It appears to me to be a whale who had an old voting slate (with yunbi/blackwave) in it, transfered all their BTS to that account, but hasnt yet updated their votes intelligently.
It doesnt seem to be a malicious attack, because they are voting for almost all the same delegates as most of the rest of us, just with a few abnormal votes like yunbi/blackwave. At worst it is someoen voting in a couple paid delegates for themself.
The amount of stake they have is about 5%, given the jump in vote counts. The large amount of additional voting is actually a good thing in many ways, since it makes it harder for anyone else to attack.
I think the best course of action is to try to inform this person that they shouldnt be voting for old paid delegates like yunbi/blackwave that gave up on their projects and have been voted out by the community.