The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Saturday, April 04, 2020

I don't quite understand this attack

Blocking ssh login attempts is working, but I have noticed another odd thing—the large number of TCP connections in the SYN_RECV state. This is indicitive of a SYN flood, but what's weird is that it's not from any one source, but scores of sources. And it's not enough to actually bring down my server.

I spent a few hours playing “whack-a-mole” with the attacks, blocking large address spaces from connection to my server, only to have the attack die down for about five minutes then kick back up from a score of different blocks. The only thing in common is that all the blocks seem to be from Europe.

And this is what I don't understand about this attack. It's not large enough to bring down my server (although I have SYN cookies enabled and that might be keeping this at bay) and it's from all over European IP space. I don't get who's getting attacked here. It could easily be spoofed packets being sent, but what's the goal here?

It's all very weird.

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