As of vsftpd version 2.0.0, SSL / TLS support is provided.The SSL / TLS support provides the ability to encrypt FTP logins and subsequentcommands, as well as the data transfers themselves. The encyption will, forexample, stop the stealing of sensitive passwords via network snooping.By default, SSL support is disabled both at compile time and at runtime.Before considering enabling / using SSL support, there are some securityconsiderations:- Only enable SSL if absolutely necessary. Enabling SSL will allow attackersto make use of any security problems in the OpenSSL libraries. Note thatthe OpenSSL libraries are a large quantity of code and have had the occasionalsecurity problem in the past.For example, your server might use virtual users to control access tonon-sensitive download content. In this case, the passwords might not beworth securing with SSL.- After enabling SSL, consider restricting access to an SSL enabled serverwhere feasible. For example, only the internal network might need access.In order to enable and use SSL support, you need the following:- vsftpd built with OpenSSL support. This is a decision your vsftpd packagermade, or if you are building vsftpd yourself, edit "builddefs.h" and change the"#undef VSF_BUILD_SSL" to "#define VSF_BUILD_SSL".- "ssl_enable=YES" in your vsftpd.conf.- A SSL certificate. By default, an RSA certificate is looked for at thelocation /usr/share/ssl/certs/vsftpd.pem. To get an RSA certificate, eitherbuy one from a certificate authority, or you can create your own self-signedcertificate. If you have OpenSSL installed, you may find a "Makefile" inyour shared certificates directory, e.g. /usr/share/ssl/certs. In that case,go to that directory and type e.g. "make vsftpd.pem". Then answer thequestions you are asked. Alternatively, read the man page for "openssl".- Also be aware of the following SSL related parameters. Read the vsftpd.conf.5manual page to learn about them: allow_anon_ssl, force_local_logins_ssl,force_local_data_ssl, ssl_sslv2, ssl_sslv3, ssl_tlsv1, rsa_cert_file,dsa_cert_file, ssl_ciphers.