There are various methods that flash videos can be copied from the web. Mostly, it requires installing software, like one of the many YouTube downloaders available. But in Ubuntu, you can directly copy and store them on your hard drive.
Whenever you watch flash-based videos on the Internet using Firefox, it gets stored in a temporary file folder on Ubuntu Lucid (10.04).
So, where does Firefox store flash in Ubuntu? After the video has finished playing, do not close your browser yet.
Finding it is simple: Just go to Places > Computer > File System > tmp folder.
Step 1 Places
Step 2 Computer
Step 3 File System
Step 4 tmp
When in the tmp folder, you'll see a file "FlashXXxx..." and that's it! Copy and save this file on your hard drive.
To play the video, download and install VLC Media Player.
Remember to delete the file after watching.