The U.S. National Security Agency has issued a cybersecurity alert about nation-state attackers targeting vulnerable VPN servers. The alert follows a similar one issued by Britain’s National Cyber Security Center last week. The NSA says attackers are actively exploiting flaws in three major VPN products: Pulse Secure, Palo Alto GlobalProtect and Fortinet Fortigate. It recommends organizations use mutual certificate-based authentication to help spot these attacks and harden their VPN servers against future attacks. Thousands of servers have not yet been patched, but thousands of servers are still not yet patched.”]