Linux Server Hack

What your [tag]Linux[/tag] Server was hacked again? I’m received a call from my friend and he said his customer Linux [tag]server[/tag] was [tag]hacked[/tag] by someone again yesterday.

After the phone conversation, I found that his Linux Server was hacked because of password [tag]brute force[/tag].

What is a brute force attack?
Brute force attack is a method of defeating a cryptographic scheme by trying a large number of possibilities; for example, exhaustively working through all possible keys in order to decrypt a message. In most schemes, the theoretical possibility of a brute force attack is recognised, but it is set up in such a way that it would be computationally infeasible to carry out. Accordingly, one definition of “breaking” a cryptographic scheme is to find a method faster than a brute force attack.


I would suggest [tag]Securing[/tag] and [tag]Hardening[/tag] Linux as below:

  • Shell access given to system administrator only
  • System administrator must have good knowledge in Networking, Security and proper training
  • Enabling password aging
  • Enforcing Stronger Passwords
  • Locking User Accounts After Too Many Login Failures
  • Avoid Easy-to-compromise User Accounts
  • Using sudo
  • Checking File Permissions and Ownership
  • Removing Unnecessary Software Packages (RPMs)
  • Using Firewall - iptables, shorewall
  • Using ChkRootkit
  • Backup your server
  • Using DenyHosts
  • Using Logwatch
  • Securing SSH - no root login, change default port no, no empty password allow
  • Using Bastille
  • Using Tripwire
  • Using Snort
  • Using SELinux
  • Using VPN
  • Patch Linux Sytem
  • Keep your system up-to-date
  • Regularly monitor the log files
  • Detect Listening Network Port
  • Secure your Application Services such as Samba, Sendmail, MySQL and etc

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