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I have a small linux server with fail2ban and UFW installed and configured behind internet gateway modem which ssh port is forwarded to server.

The attackers are discovering by fail2ban and added to iptables and information mail is sent to me, but attackers can continue to attacks. When I ban manually remote IP from UFW, attackers are continue to attacks, too. After all I keep receiving those fail2ban information mails once about an hour from fail2ban

For example the 46.249.65.54 hostile IP is keep attacking to server while the IP registered to iptables. Here are the IP tables entries:

# iptables -L
Chain INPUT (policy DROP)
target     prot opt source               destination         
f2b-sshd   tcp  --  anywhere             anywhere            
ufw-before-logging-input  all  --  anywhere             anywhere            
ufw-before-input  all  --  anywhere             anywhere            
ufw-after-input  all  --  anywhere             anywhere            
ufw-after-logging-input  all  --  anywhere             anywhere            
ufw-reject-input  all  --  anywhere             anywhere            
ufw-track-input  all  --  anywhere             anywhere            
DROP       all  --  astaroth.visao.psi.br  anywhere            
DROP       all  --  177.152.35.7         anywhere            

Chain FORWARD (policy DROP)
target     prot opt source               destination         
ufw-before-logging-forward  all  --  anywhere             anywhere            
ufw-before-forward  all  --  anywhere             anywhere            
ufw-after-forward  all  --  anywhere             anywhere            
ufw-after-logging-forward  all  --  anywhere             anywhere            
ufw-reject-forward  all  --  anywhere             anywhere            
ufw-track-forward  all  --  anywhere             anywhere            

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
ufw-before-logging-output  all  --  anywhere             anywhere            
ufw-before-output  all  --  anywhere             anywhere            
ufw-after-output  all  --  anywhere             anywhere            
ufw-after-logging-output  all  --  anywhere             anywhere            
ufw-reject-output  all  --  anywhere             anywhere            
ufw-track-output  all  --  anywhere             anywhere            

Chain f2b-sshd (1 references)
target     prot opt source               destination         
REJECT     all  --  46-249-65-54.net1.bg  anywhere             reject-with icmp-port-unreachable
RETURN     all  --  anywhere             anywhere            

Chain ufw-after-forward (1 references)
target     prot opt source               destination         

Chain ufw-after-input (1 references)
target     prot opt source               destination         
ufw-skip-to-policy-input  udp  --  anywhere             anywhere             udp dpt:netbios-ns
ufw-skip-to-policy-input  udp  --  anywhere             anywhere             udp dpt:netbios-dgm
ufw-skip-to-policy-input  tcp  --  anywhere             anywhere             tcp dpt:netbios-ssn
ufw-skip-to-policy-input  tcp  --  anywhere             anywhere             tcp dpt:microsoft-ds
ufw-skip-to-policy-input  udp  --  anywhere             anywhere             udp dpt:bootps
ufw-skip-to-policy-input  udp  --  anywhere             anywhere             udp dpt:bootpc
ufw-skip-to-policy-input  all  --  anywhere             anywhere             ADDRTYPE match dst-type BROADCAST

Chain ufw-after-logging-forward (1 references)
target     prot opt source               destination         
LOG        all  --  anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-after-logging-input (1 references)
target     prot opt source               destination         
LOG        all  --  anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-after-logging-output (1 references)
target     prot opt source               destination         

Chain ufw-after-output (1 references)
target     prot opt source               destination         

Chain ufw-before-forward (1 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED
ACCEPT     icmp --  anywhere             anywhere             icmp destination-unreachable
ACCEPT     icmp --  anywhere             anywhere             icmp source-quench
ACCEPT     icmp --  anywhere             anywhere             icmp time-exceeded
ACCEPT     icmp --  anywhere             anywhere             icmp parameter-problem
ACCEPT     icmp --  anywhere             anywhere             icmp echo-request
ufw-user-forward  all  --  anywhere             anywhere            

Chain ufw-before-input (1 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED
ufw-logging-deny  all  --  anywhere             anywhere             ctstate INVALID
DROP       all  --  anywhere             anywhere             ctstate INVALID
ACCEPT     icmp --  anywhere             anywhere             icmp destination-unreachable
ACCEPT     icmp --  anywhere             anywhere             icmp source-quench
ACCEPT     icmp --  anywhere             anywhere             icmp time-exceeded
ACCEPT     icmp --  anywhere             anywhere             icmp parameter-problem
ACCEPT     icmp --  anywhere             anywhere             icmp echo-request
ACCEPT     udp  --  anywhere             anywhere             udp spt:bootps dpt:bootpc
ufw-not-local  all  --  anywhere             anywhere            
ACCEPT     udp  --  anywhere             224.0.0.251          udp dpt:mdns
ACCEPT     udp  --  anywhere             239.255.255.250      udp dpt:1900
ACCEPT     igmp --  anywhere             base-address.mcast.net/4 
ufw-user-input  all  --  anywhere             anywhere            

Chain ufw-before-logging-forward (1 references)
target     prot opt source               destination         

Chain ufw-before-logging-input (1 references)
target     prot opt source               destination         

Chain ufw-before-logging-output (1 references)
target     prot opt source               destination         

Chain ufw-before-output (1 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED
ACCEPT     igmp --  anywhere             base-address.mcast.net/4 
ufw-user-output  all  --  anywhere             anywhere            

Chain ufw-logging-allow (0 references)
target     prot opt source               destination         
LOG        all  --  anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW ALLOW] "

Chain ufw-logging-deny (2 references)
target     prot opt source               destination         
RETURN     all  --  anywhere             anywhere             ctstate INVALID limit: avg 3/min burst 10
LOG        all  --  anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-not-local (1 references)
target     prot opt source               destination         
RETURN     all  --  anywhere             anywhere             ADDRTYPE match dst-type LOCAL
RETURN     all  --  anywhere             anywhere             ADDRTYPE match dst-type MULTICAST
RETURN     all  --  anywhere             anywhere             ADDRTYPE match dst-type BROADCAST
ufw-logging-deny  all  --  anywhere             anywhere             limit: avg 3/min burst 10
DROP       all  --  anywhere             anywhere            

Chain ufw-reject-forward (1 references)
target     prot opt source               destination         

Chain ufw-reject-input (1 references)
target     prot opt source               destination         

Chain ufw-reject-output (1 references)
target     prot opt source               destination         

Chain ufw-skip-to-policy-forward (0 references)
target     prot opt source               destination         
DROP       all  --  anywhere             anywhere            

Chain ufw-skip-to-policy-input (7 references)
target     prot opt source               destination         
DROP       all  --  anywhere             anywhere            

Chain ufw-skip-to-policy-output (0 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            

Chain ufw-track-forward (1 references)
target     prot opt source               destination         

Chain ufw-track-input (1 references)
target     prot opt source               destination         

Chain ufw-track-output (1 references)
target     prot opt source               destination         
ACCEPT     tcp  --  anywhere             anywhere             ctstate NEW
ACCEPT     udp  --  anywhere             anywhere             ctstate NEW

Chain ufw-user-forward (1 references)
target     prot opt source               destination         

Chain ufw-user-input (1 references)
target     prot opt source               destination         
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssh /* 'dapp_OpenSSH' */
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssh /* 'dapp_OpenSSH' */
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:nfs
ACCEPT     udp  --  anywhere             anywhere             udp dpt:nfs
ACCEPT     udp  --  anywhere             anywhere             multiport dports netbios-ns,netbios-dgm /* 'dapp_CIFS' */
ACCEPT     tcp  --  anywhere             anywhere             multiport dports netbios-ssn,microsoft-ds /* 'dapp_CIFS' */
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:6600 /* 'dapp_MPD' */
DROP       all  --  astaroth.visao.psi.br  anywhere            
DROP       all  --  177.152.35.7         anywhere            
DROP       all  --  46-249-65-54.net1.bg  anywhere            

Chain ufw-user-limit (0 references)
target     prot opt source               destination         
LOG        all  --  anywhere             anywhere             limit: avg 3/min burst 5 LOG level warning prefix "[UFW LIMIT BLOCK] "
REJECT     all  --  anywhere             anywhere             reject-with icmp-port-unreachable

Chain ufw-user-limit-accept (0 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            

Chain ufw-user-logging-forward (0 references)
target     prot opt source               destination         

Chain ufw-user-logging-input (0 references)
target     prot opt source               destination         

Chain ufw-user-logging-output (0 references)
target     prot opt source               destination         

Chain ufw-user-output (1 references)
target     prot opt source               destination         

Why those IP's are not stay banned? And why they can still reach to server?

Required information:

Full Fail2Ban configuration

SSHD Jail Conf

  • How are you discovering that they are not getting blocked? What logs? Because the blocking tech you have is on the server itself, nothing is preventing the attackers from actually reaching your server. – schroeder Mar 15 '17 at 8:08
  • The Fail2Ban is keep sending mails about permanently banned IP via UFW. This is why I think they are not blocked. – Sencer H. Mar 15 '17 at 8:14
  • 1
    but, you are getting informed that an IP is blocked ... so, they are blocked ... – schroeder Mar 15 '17 at 8:17
  • 1
    I think you need to verify the into that is in the alert emails and your alert conditions. Are you getting informed that the IP is getting newly added to the block, or are you getting informed that an already blocked IP is trying to attack? If they are already blocked, there is no problem, you are just getting informed when you don't want to be. – schroeder Mar 15 '17 at 8:19
  • Fail2Ban is keep sending 'The IP 46.249.65.54 has just been banned by Fail2Ban after 3 attempts against sshd.' mails. – Sencer H. Mar 15 '17 at 8:36

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