An X.509 certificate is a vital safeguard against malicious network impersonators. Without x.509 server authentication, man-in-the-middle attacks can be initiated by malicious access points, compromised routers, etc.  

*** This is a Security Bloggers Network syndicated blog from PKI Blog authored by Ryan Yackel. Read the original post at: https://blog.keyfactor.com/what-is-x509-certificate