Use secure applications and protocols
Certain protocols that have been around since the start of the internet (such as HTTP, FTP, ...) did not take into account the need to respect the confidentiality, integrity and availability (CIA) of transmitted information (e.g. by using non-hidden passwords or reproducing a transaction that was supposed to be unique).
Moving to secured and up-to-date versions of the main protocols (e.g. SFTP/FTPS, HTTPS with TLS, ...) alleviates alot of security issues.