Question

How to close port in Centos

Asked by: remoteuser

Hi
I want to close and open port in CentOS 5.2  and how to Restrict the port TCP 21 to only allowed IP address. I checked the ftp config file but I don't have vsftpd. It is a virtual hosting server and control by Plesk control panel.

Thanks



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Asked On
2009-07-22 at 20:47:44ID24593402
Topics

Linux Administration

,

CentOS

Participating Experts
3
Points
500
Comments
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Answers

 

by: remoteuserPosted on 2009-07-22 at 20:52:32ID: 24921673

One more thing I forgot to add I want to penetration test to my server and new for this, except nmap what toll use to generate security report.. Is it possible to get some sample pen test report

Thanks
 

 

by: fosiul01Posted on 2009-07-23 at 00:30:13ID: 24922555

You can do this way :

Block every ports and open one by one

example


iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -A INPUT --source xx.xx.xx.xx -p tcp --dport 21 -j ACCEPT
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT


so this rules
iptables -A INPUT --source xx.xx.xx.xx -p tcp --dport 21 -j ACCEPT

will only allow from xx.xx.xx.xx ip, and will block everything

You can use

netstat -an or lsof -i:TCP
lsof-i:UDP

to see what tcp or udp ports are listenning.

also you can use some external website to check which ports are open in your server

 

by: mrwortaPosted on 2009-07-23 at 06:00:08ID: 24924594

Using "netstat -lnp" you will see which pid/process is
listening on which port and you could disable
any unneeded service using "chkconfig".

The syntax for the current version of lsof is without the ":"

lsof -i UDP
lsof -i TCP

Do you have a license for the Plesk Firewall Module?




 

by: KeremEPosted on 2009-07-23 at 08:17:17ID: 24926166

Hi,

I'll suggest to use vsftpd. With vsftpd you can automatically generate iptables rules. So that if someone tries to access to your ftp server repeatedly.

You just add a section on your vsftp configuration file such as this and it will bloct any IP which tries to access your FTP server with more than 5 wrong passwords fo some definite time. It is 120 seconds in my example. Of coure this is  an example and you can modify it to impose your own policy.

Cheers,
K.
 

[vsftpd-iptables]
 
enabled  = true
filter   = vsftpd
action   = iptables[name=VSFTPD, port=ftp, protocol=tcp] hostsdeny
logpath  = /var/log/vsftpd.log
maxretry = 5
bantime  = 120
                                              
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by: remoteuserPosted on 2009-07-23 at 17:06:04ID: 24931368

Hi Mrworta
I have licence for plesk firewall.

Thanks

 

by: KeremEPosted on 2009-07-24 at 00:51:54ID: 24932861

Hi,

I'm a security expert myself (CISSP, CISA). I do penetration test for companies for years now. The best tool I use around is Nessus. It is free. The reports are quite detailed.

Cheers,
K.

 

by: remoteuserPosted on 2009-07-26 at 18:09:33ID: 24948279

Hi KeremE

Thank you very much for your information. I install neussus in my Linux system now I want to scan my remote web server. Do i need to install on remote server too or I can able to scan as nmap do.
could you please provide me some commands to test security vulnerabilities.

Thanks

20120131-EE-VQP-002

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