Take a look at the state of RPKI. ROA validation is common these days, and ASPA validation will be common soon. You still need to manually validate that your peer truly represents the AS that they claim to, but if that's been done, ROA+ASPA validation prevents unauthorized announcements.

Absent RPKI, people have been filtering based on IRR for ages, which will not necessarily prevent unauthorized announcements, but will require an attacker to leave a paper trail when making one.