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Security

I am trying to set exec-shield protection on Linux as described here but getting the following error on Ubuntu Linux server version 12.04 LTS:

sysctl -w kernel.exec-shield=1
error: "kernel.exec-shield" is an unknown key

How do I fix this problem and make sure exec-shield buffer overflow protection security feature turned on Ubuntu Linux?
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My iptables based firewall allows only port TCP 80 and 443. I also need tcp port # 22, but I do not have static IP at my home. How do I open and close TCP port #22 on demand under Debian or Ubuntu Linux based server systems? How do I install a port-knock server called knockd and configure it with iptables to open tcp port #22 or any other ports?

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I am the small business owner and runs my own web-site. I have noticed increased cracking activity against by blog. What's the best way to block WordPress URLs such as example.com/blog/wp-login.php and example.com/blog/wp-admin/ in the nginx web-server?
Tutorial details
DifficultyAdvanced (rss)
Root privilegesYes
RequirementsLinux+Nginx
Estimated completion timeN/A

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Linux: Turn On TCP SYN Cookie Protection

I am under DoS attack. My cloud based server hosting company asked me to enable TCP SYN cookie protection to save my domain from SYN Attack. How do I turn on TCP Syn cookie protection under Ubuntu or CentOS Linux based server?
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Linux Iptables Setup Firewall For a Web Server

I have setup an Apache web server on CentOS Linux. How do I configure firewall to allow or block access? How do I setup firewall for a web server under RHEL or CentOS Linux v6.x?
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I have Soekris single board communication embedded computers which is optimized for low power and network usage. The server has four Ethernet ports. How do I setup IPv4 software bridge using OpenBSD operating systems so that the rest of four ports act as a network switch?
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AppArmor ("Application Armor") is a security module for the Linux kernel and integrated into both kernel and Ubuntu Linux. How do I disable AppArmor protection for mysql profile / service under Ubuntu or Novell Suse Enterprise Linux?
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