The Cisco ASA contains a builtin scp server. By enabling that you can use the scp protocol to transfer files to and from the server using an scp client.
scp is a secure file transfer protocol. It is almost like ftp but it runs over ssh. So in order to enable the scp server in the firewall you must first enable ssh access from the client to the firewall (creating rsa keys, allowing source ip to manage firewall using ssh and so on). When that is done the scp server can be enabled with the command… “scp server enable” (duh!).
Now you can use the scp client in your machine to copy files to and from the firewall flash in a secure way!
Look at this video where I explain and demonstrate the feature.