How To Install DenyHosts on CentOS 7

We explain all the steps you need to install DenyHosts in CentOS 7 and avoid attacks to the ssh

What is DenyHosts?

DenyHosts is a script that is used by many administrators and IT staff to avoid attacks on SSH servers, which can be known as dictionary-based or brute-force attacks because of the ability to decrypt the password.

As administrators, we can visualize in the CentOS 7 route the access attempts that have occurred to the system, and although as a general rule these accesses were not satisfactory it is better to prevent this type of efforts since some of them can occur and have serious security flaws.


Install DenyHosts in CentOS 7

First of all, we recommend updating the system using the command:

sudo yum update

Once the system is upgraded, we proceed to download the DenyHosts elements from the official repositories using the following command:

sudo rpm -Uvh

Next we will install the DenyHosts packages using the following command:

sudo yum install denyhosts

Configure Parameters DenyHosts

Access the following route:

sudo nano /etc/hosts.allow

There it is necessary that we enter the IP address of our team, in this case it is at the end of the file using the SSHD parameter:


Save Changes: Ctrl + O

Exit the editor: Ctrl + X

Then we will access the following file for its edition:

sudo nano /etc/hosts.deny

There we must add the next line to the end of the file:

sshd: ALL **

Save the changes. Once applied these changes we will use the following command to restart the service:

/etc/init.d/denyhosts restart

Main Configuration DenyHosts

Finally we can access the next route to adjust all DenyHosts values:

sudo nano /etc/denyhosts.conf

We will see the following:

There we can configure values such as:

PURGE_DENY: It allows us to define the time in which the IP addresses that have been blocked will be deleted.

BLOCK_SERVICE: Using this option we can define what services will be blocked to those devices that try to access without authorization.

DENY_THRESHOLD_INVALID: Using this alternative we can define the number of failed attempts of an account that does not exist

DENY_THRESHOLD_VALID: It does the same job as DENY_THRESHOLD_INVALID = but only for root users.

ADMIN_EMAIL: Through this option, we can define an email to receive reports about failed connections.

In the same way we can configure the parameters according to our needs.

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