The default in later OpenSSH is 6, which seems too high. If you can't
get your password correct after 3 tries then I think you need help.
Eventually I'd like an easy way to enable blocking of repeated login
attempts at the firewall level. I think it's possible in firewalld.
I had removed them from Debian 8 and Ubuntu 14.04 configs last year
when the NSA's Suite B crypto guidelines dropped 128-bit algorithms
but those changes didn't make it to my new Ubuntu 16.04 config.
It is probably overkill and paranoid, but this server is mine, so I
can make those decisions (and I only connect from modern clients).
