From the HP site:
HP SWFScan, a free tool developed by HP Web Security Research Group, will automatically find security vulnerabilities in applications built on the Flash platform.
- Download and install SWFScan from http://www.hp.com/go/swfscan.
- Run SWFScan.
- Click the Settings button. The Settings dialog box displays.
- Select the Checks tab. Then just click on each one of the items to read about the vulnerability and the potential fix for it.
The tool runs on Windows only.
You just point it at a file or URL, and it will decompile it. It will also analyze the swf to detect any embedded URLS, and more importantly any potential security threats (Database connection strings, passwords, debug messaging, cross site scripting vulnerabilities, etc..). This could be useful if you are auditing applications, or if you are inheriting a legacy application and want to find any weaknesses in it.