Re: Thousands of login attempts

[Dimitar Katerinski]

@lbutlr wrote:
/etc/hosts.allow:
    ALL : 185.103.253.246 : DENY
Has no effect.

I would suggest using your firewall utility to block this on tcp/ip 
level. If you are running Postfix under Linux
the following iptables command should block this IP to accessing your 
smtp service on port 25:
iptables - I INPUT -s 185.103.253.246 -p tcp --dport 25 -j DROP

As someone already suggested - have a look at fail2ban.

Cheers,
Dimitar