You can modify settings for Yahoo domain names in the Yahoo Domain Control Panel, which allows you to enable Domain Locking. With this feature enabled, absolutely no changes (other than yearly renewal) can be made to the status or technical information of the domain without your explicit consent - not even by you (until you turn off Domain Locking).
Aside from registration your domain through a trusted registrar such as Yahoo Domain, you can also take help prevent domain hijacking by using private registration to hide your domain's administrative contact information. If the administrative email address is publicly available, then a potential hijacker has two important pieces of information - the domain name, and the administrator's email address. If they can then gain access to the administrative email address, they can modify domain settings.
