Which is NOT a secure method of transferring sensitive information online?

Sending an email without encryption is not a secure method of transferring sensitive information online. When an email is sent without any form of encryption, it can be easily intercepted and read by unauthorized individuals. Standard email protocols do not protect the contents of the message while it is in transit; therefore, any sensitive information included in the email can be compromised.

In contrast, using a virtual private network (VPN) creates a secure tunnel for internet traffic, protecting data from eavesdroppers. Secure websites that use HTTPS encrypt data during transmission, ensuring that sensitive information, such as credit card details or personal data, remains private. Encrypted messaging apps also provide security by encrypting messages on both ends, making interception by third parties virtually impossible. Thus, the lack of any encryption in an unprotected email transmission makes it the least secure option among the methods listed.