One of the best ways to protect sensitive computer data like credit card numbers and social security information is to use encryption software. Encryption software executes an algorithm that is designed to encrypt data in such a way that it cannot be recovered (decrypted) without access to the key. It is a main component of all aspects of file protection and computer communication. Files on hard drives and other removable media, email messages, and packets sent over computer networks can be made secure by encryption software.
For those of you who are interested, here's a list of well-known free and open source encryption software for Linux:

TrueCrypt

TrueCrypt is one of the most popular disk encryption tools around. It can encrypt and decrypt files on-the-fly (real-time) as needed without user intervention beyond entering the passphrase. TrueCrypt is capable of creating a virtual encrypted disk within a file or a device-hosted encrypted volume on either an individual partition or an entire storage device. It currently uses the XTS mode of operation but is backward compatible with older volumes.

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