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Display List of updated software ( Security fix) yum list updates Or yum check-update Patch up system by applying all updates yum update List all installed packages rpm -qa How to find a perticular installed packages( httpd) rpm -qa | grep httpd How to look update for specific packages yum update {package-name-1} To check for [...]

Problem: If vsftpd failed to retrieves directory listing then do the following: In vsftpd.conf pasv_min_port=x example : [ pasv_min_port=1023] pasv_max_port=x example : [pasv_max_port=1050] Now add port 1023-1050 in iptables iptables -A INPUT –source xx.xx.xx.xx -p tcp –dport 1023:1050 -j ACCEPT it will allow filezilla to connect to ftp server via passive mode.

useradd -s /sbin/nologin username : It will prevent user to login to server userdel -r username: -r delete everything( home directory,mail spool) without -r it will just delete account references from user and groups usermod -L username : -L to disable user account usermod -U username : -U enable the user account. echo ‘mypassword’ | [...]

Ref :http://hostingfu.com/article/ssh-dictionary-attack-prevention-with-iptables Last week (9-15 April). 8,750 failed SSH login attempt, averaging almost one per minute, trying out all kinds of possible user names and left tons of junk in my message log. The recent SSH brute-force attacks (actually it’s not that recent) are rather annoying, and this article at Whitedust.com has useful information on [...]

Allow ssh connection from selected Ip: iptables -A INPUT –source xx.xx.xx.xx -p tcp –dport 22 -j ACCEPT iptables -A INPUT –source yy.yyy.yy.yy -p tcp –dport 22 -j ACCEPT iptables -A INPUT -p tcp –dport 22 -j DROP Only allow ssh to linux box: iptables -P INPUT DROP iptables -P OUTPUT DROP iptables -P FORWARD DROP [...]