Senf, the Sensitive Number Finder, is a little handy tool written by the information security group at the University of Texas at Austin. Senf will search your hard drive for files containing Social Security Numbers and Credit Card Numbers. Once these files are found, you can decide what to do. You may want to wipe them or encrypt them to keep your sensitive information from being snagged by a computer virus or trojan, or in case you loose your laptop or portable device.
You can refer to my Blog on encryption Encrypting your USB drive [1] if you want to encrypt the data or you can refer to my Free cool software, Part 1 - Open Source [2] if you want to securely and permanently erase the files you found.
Be sure to read the Senf Readme [3] and to learn what Senf IS and and what it IS NOT.
Links:
[1] http://hamptonroads.com/2007/10/encrypting-your-usb-drive
[2] http://hamptonroads.com/2007/09/free-cool-software%2C-part-1-open-source
[3] https://source.its.utexas.edu/groups/its-iso/projects/senf/wiki/SenfReadme