Set ban correctly

src/Dockerfile

@@ -32,7 +32,8 @@ COPY proftpd.conf /etc/proftpd/proftpd.conf
 RUN useradd -r -s /bin/false ${FTP_USER}
 
 # Create a directory for FTP and set permissions
-RUN mkdir -p /var/ftp && \
+RUN mkdir -p /var/ftp/ && \
+    touch /var/ftp/ban.tab && \
     chown -R ${FTP_USER}:${FTP_GROUP} /var/ftp
 
 # Generate self-signed SSL certificate

src/proftpd.conf

@@ -10,6 +10,7 @@ DefaultServer on
 LoadModule mod_tls.c
 LoadModule mod_sql.c
 LoadModule mod_sql_mysql.c
+LoadModule mod_ban.c
 
 # Port 21 is the standard FTP port.
 Port 21
@@ -83,13 +84,20 @@ AuthPAM off
 </Limit>
 
 <IfModule mod_ban.c>
+  # Set maximum login attempts per connection
+  MaxLoginAttempts 1
+
   BanEngine on
   BanLog /var/log/proftpd/ban.log
+  BanTable /var/ftp/ban.tab
+
+  # Ban IP addresses that reach MaxLoginAttempts 5 times in 10 minutes, for 1 hour
+  BanOnEvent MaxLoginAttempts 5/00:10:00 01:00:00
 
-  # Ban IP addresses that fail authentication 5 times in 10 minutes
-  BanOnEvent BadPassword 5/00:10:00 00:60:00
+  # Instantly ban anonymous login attempts
+  BanOnEvent AnonRejectPasswords 1/00:00:01 99:99:99
 
   # Control connection policy
-  BanControlsACLs all allow user root
-  BanControlsACLs all deny all
+  BanControlsACLs all allow user proftpd_user
+  BanMessage "Host %a has been banned"
 </IfModule>