Spider--an open-source forensic tool from Cornell University--scans your hard drive, Web site, or other collection of files to identify confidential data such as SSNs, credit card account numbers, and bank account routing numbers. When a scan is complete, Spider produces a list of files that may potentially contain confidential data. You must review the log file to ensure that Spider did not identify any false positives.
You can then use Spider to securely move or erase files, move files to the trash, or mark the file as a false positive. Download Spider and its accompanying documentation from Cornell's Web site.