My address received this strange transaction lately. However, that address has not been written anywhere so the attacker had to just discover it from the block chain I suspect. Another theory is that this is some kind of bitcoin terrorism. People who have nice round balances in their cold storage get them ruined.
There are some interesting public notes there:
Public Note: Hey, give me back my 20 Bitcoin
Public Note: If you are reading this, please take some time to remember those who died 12 years ago today in the WTC attacks
Public Note: Whoever you are, you're epic.
edit:
there's some more suspicious activity, look this address:
https://blockchain.info/address/1AgesqfafUHHpAWnmjj9g6TVqBGXk4ixxgA lot of coins are sent to all possible addresses that start with 1Ag
According to Mendelejev's table, silver is Ag.
ONE MORE THEORY:
What if the attacker has targeted just one address? However, to make it less threatening it has added a bunch of other random addresses to the formula? Then people such as myself who get disturbed by this activity start making posts to this thread and are immediately connected to their address by the forum user.
and one more:
Some of the destination addresses have spent their input except this suspicious input. Maybe the attacker tries to pin point automated wallets? So if the suspicious input remains unspent but other balance is spent then there could be some automation in place which could be abused with the transaction malleability vulnerability.