Data Channel Protection Level (PROT) - KB Article #1479Related Articles --
After successfully negotiating a protection buffer size, an FTP client might issue the PROT command. The PROT command is used to specify the level of protection used on the data channel. The four levels of protection (in order of security) are defined as "Clear", "Safe", "Confidential", and "Private".
If no PROT command is issued, the data channel will be clear and raw data will be transferred over the data channel. For complete security, a level of "private" should be used which encrypts the data channel and ensures its integrity. Supported levels of protection are defined by the security mechanism specified in the AUTH command that initially secured the command channel. Not all levels of protection may be supported by each security mechanism.