"SCP" commonly refers to both the Secure Copy Protocol and the program itself. According to OpenSSH developers in April 2019, SCP is outdated, inflexible and not readily fixed; they recommend the use of more modern protocols like SFTP and rsync for file transfer.

Is SCP still secure?

Although SCP is generally considered a secure option for transferring files between remote hosts, Harry Sintonen, a security researcher with Finnish cyber-security firm F-Secure, discovered in January 2019 that the protocol is vulnerable.

Is SCP reliable?

An initial evaluation of SFTP and SCP would indicate that both protocols are equally secure as both use SecureShell as the encryption platform for data in transit. In 2019, this was not the case (assuming all SCP clients are not patched at this point).