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Security

Linux / UNIX: Encrypt Backup Tape Using Tar & OpenSSL

How do I make sure only authorized person access my backups stored on the tape drives (DAT, DLT, LTO-4 etc) under Linux or UNIX operating systems? How do I backup /array22/vol4/home/ to /dev/rmt/5mn or /dev/st0 in encrypted mode?
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Nginx Block And Deny IP Address OR Network Subnets

How do I block or deny access based on the host name or IP address of the client visiting website under nginx web server?
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Linux Default Services Which Are Enabled at Boot

Can you provide a guidance on default CentOS / Fedora / RHEL / Redhat enterprise Linux services which are enabled at boot time by a default? Can you provide set of recommendations for all default services and which to keep for performance and security and which to turn off?
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CentOS / Redhat: Turn On SELinux Protection

SELinux enforces the idea that programs should be limited in what files they can access and what actions they can take. However, by default it is turned off under RHEL / CentOS 5.x server? How do I turn it on? How can I enable SELinux on CentOS / RHEL 6 IBM server?
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Linux: Create /tmp And Mount as Partition File With the noexec, nosuid, And nodev

How do I mount /tmp as a separate filesystem (/root/images/tmpfile.bin) with the noexec,nosuid, nodev options under Linux like operating systems?
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Mac OS X Disable Unnecessary Services

How do I disable unnecessary services under Mac OS X to secure my Mac OS X based desktop / server / laptop?
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I‘ve brand new Ubuntu Linux server (Apache + PHP5 FastCGI + Lighttpd image only server) installed for my wordpress, mediawiki and vBullietin software. I can load forntpage of all software but user cannot edit any wiki pages or post anything and I get the following error in log file:

PHP Fatal error: Allowed Memory Size of 20971520 Bytes exhausted (tried to allocate 131072 bytes) in /usr/share/mediawiki/includes/OutputHandler.php on line 81

How do I fix this problem?
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CentOS / Redhat Apache mod_ssl Configuration

The mod_ssl module provides strong cryptography for the Apache Web server via the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols. How do I install and configure mod_ssl under CentOS / Fedora / Redhat Enterprise Linux?
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Mac OS X Display Access Warnings Message For The Login Window

I know how to display notice of a computer’s ownership, to warn against unauthorized access, under Linux gnome desktop. How do I display similar message under Apple Mac OS X to remind authorized users of their consent to monitoring?
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Linux Upgrade Password Hashing Algorithm to SHA-512

The default algorithm for storing password hashes in /etc/shadow is MD5. I was told to use SHA-512 hashing algorithm. How do I set password hashing using the SHA-256 and SHA-512 under CentOS or Redhat Enterprise Linux 5.4?
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