ResEdit Information:
ResEdit is a utility intended for use by developers to manipulate resources within a file. Use of this application is not recommended unless you have a strong knowledge of how the Macintosh operating system functions. NOTE: if this software is improperly used, it is possible to incur data loss and/or render your Macintosh computer unusable, thus requiring you to reinstall the Mac OS

ResEdit WebSite:
ResEdit is an Apple product and is currently at version 2.1.3.
Access on:
Apple Software Update Page

This software is Free.

ResEdit Uses:
As stated above, ResEdit is useful for editing resources in applications and documents. This can render insecure a 'secure' computer because a user can change resources within an application, or open a 'security' application and look for the password resources. They can add new or modify current resources, causing the system or program to crash. Files can be made visible/invisible by setting their information flags. So if you are running a Key Stroke Logger like Invisible Oasis, you can rename the extension to something like 'Monitor Depth' and make the extension invisible. It would be less likely be noticed. If you use extension manager you will see all extensions even if they are invisible, but by renaming it to a system sounding extension, it won't be that noticeable. So system admins, check for Key Stroke Loggers if you think a user knows your passwords.