Destination port 6881 is BitTorrent. You will get a huge flood of attempted UDP and TCP connections on the designated bittorrent listening port whenever you are using bittorrent.
I seem to get an occasional, large increase in malicious scan attempts once my IP has been logged to a BitTorrent tracker. Seems like an obvious place to find IPs to scan but I do not know the details of the BitTorrent protocol, so my theory is only a guess.
You might post the entire log entry, since you cut off the beginning of the line.