The document was posted to a public site as part of a contract bidding process. Info about passenger screening, checking for weapons and other confidential security-related items were supposed to be removed. But rather than actually remove the text, TSA just covered it with black boxes.

Computer savvy folks were able to read the manual and its security process details, Computerworld reports.

The TSA’s mistakes offer up a grim reminder to anyone who isn’t well versed in the complexities of electronic document redaction, the art – and science – of blacking out information that should not be seen.

A big problem with redaction: Few folks understand how it works.

If you’re redacting hard copy, you can take a permanent, black magic marker and cover the data or text with bold strokes. Not on digital text.

The text may not be viewable, but it can be indexed, which makes it searchable and simple to retrieve by copying and pasting blacked-out portions to another document.

•Also, the metadata that’s embedded in documents isn’t disturbed by blacking out text. It’s still in the document and can be retrieved.

The key to redacting information so that it can’t be unearthed? Remember these rules:

1. Never use word processing for redaction. Even Adobe’s Professional Edition might not be safe. Keep document creation and redaction separate, and
2. Use strong, automated redaction tools that not only search and eradicate text but also its metadata.