Brute force

A Brute force attack is an attempt by an internet user attemptiing to gain unauthorized access to your server by way of connecting to it, by using a dictionary file to attempt rapid logins. The dictionary file contains a list of user names and/or passwords, and a programme or script attempts multiple logins per second, trying if they could gain access.

How to prevent Brute Force Attack?

The most efficient method to prevent Brute Force Attack is to use BFD ( Brute Force Detection).

Linux servers runnig on cpanel is preinstalled with BFD. It works by watching various log files which maintained by various services includind failed login attempts. If it detects several failed login attempts in a short period time from the same source IP adress, BFD blocks that IP adress in the server’s firewall.

Enabling BFD in Cpanel servers

You can view or modify the BFD settings by in your WHM.

1)Login to your WHM.

2)Click on the Security center.

3)Find cPHULK Brute Force Protection and navigate to the link.

4)You can configue cPHULK BFD configuration here.

A sample configuration is shown here.

Confguration settings

IP based Brute Force protection period in minutes:			  	10
Brute Force protection period in minutes:					5
Maximum Failures by account:					  	20
Maximum Failures per IP:						  	5
Maximum Failures per IP before IP is blocked for two week period:	35

check the (Extended account lockout time upon additional authentication failures)

Disable BFD

It is sometimes a great issue when the legitimate IP is blocked by BFD. You can simply disable cPHULK to avoid this

1)Login to WHM.

2)click on the secrity center.

3)Navigate ot “cPHULK Brute Force Protection” link

4)Locate the “cPHULK is currently Enabled” and click the “Disable” button

5)Finally, click the “Flush DB” button to purge previous records

What should be done when your ip has been blocked by BFD?

The first method was to disable Brute Force and clear out the block by using the “Flush DB” option, but it’s a little risky method because BFD is turned off. Another bettrer option without diabling BFD is mentioned here.

This is by manually clearing tables in mysql. cPHULK stores all of its information in a database called cphulkd. There are two tables of intrest which are logins and brutes. The logins table stores login authenticaion failures. The burtes table stores excessive authenticaion failures indicative of brute force attack. We have to use mysql to see the list.

[you@yourserver~]$  mysql -u user -p ******
mysql> connect cphulkd
mysql> select IP, BRUTETIME from brutes order by BRUTETIME;
mysql> select IP, LOGINTIME FROM logins order by LOGINTIME;

This will give you a list of the IP’s and the LOGINTIME thet were entered inot the database

While still connected to the database through the MySQL monitor, we can clear trables by running some simple commands.

mysql> delete from brutes;
Query OK, 0 rows affected (0.00 sec)
mysql> delete from logins;
Query OK, 32 rows affected (0.00 sec)

Now, log back to the account.