I have a bit of an issue, this has caught my attention yesterday. Someone or something, a botnet I presume, has been trying to gain access to specific e-mail addresses.
The server software keeps blocking the login attempts but the problem is that I keep getting more and more hits. The IPs are not from one specific range but from all over the world.
There are a little over 500 attempts since Feb 26th. Is there anything I can do to block this "attack" besides blocking the IPs after an X amount of attempts?
I am running a CentOS server with Direcadmin installed. I use csf+lfd as a add-on.