How to find credit card numbers and social security numbers on an employee workstation
Cornell developed their spider program a while ago. You can search for anything on a machine using regular expressions with this tool. It takes a bloody long time to search an entire hard drive so hopefully you have the user locked down to write access in My docs or the equal on linux/osx. This tool has to run as administrator or a service on newer versions of windows so plan accordingly when automating.
I use this to search for HIPAA data and credit cards. Works pretty well, I write the log file out to a server over an IPsec encrypted tunnel. Download and enjoy: