I don't know how your server is being flooded by fake players..
However try setting sv_maxconnperip to 2 or 3 in your server.cfg and restart your server afterwards.
(These are the maximum amount of connections able to connect to your server from the same IP)
Code:
seta sv_maxconnperip "2"
If that doesn't help, you could try Reborn's packet anti-flood. Also a cvar to switch on in your server.cfg (and restart server afterwards).
(Will block packets from coming in when being flooded for x amount of time)
Code:
seta sv_packetantiflood "1"