NSA, CISA share VPN security tips to defend against hackers

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) and the National Security Agency (NSA) have released guidance for hardening the security of virtual private network (VPN) solutions.

The two agencies created the document to help organizations improve their defenses particularly against attacks from nation-state adversaries, who in the past have exploited bugs in VPN systems to “steal credentials, remotely execute code, weaken encrypted traffic’s cryptography, hijack encrypted traffic sessions, and read sensitive data from the device.”The document provides direction for selecting VPN solutions that follow the industry standards and the best practices for using strong authentication credentials.

Organizations should also choose products from reputable vendors with a history of acting quickly to patch known vulnerabilities.

As general rules for hardening the VPN, the two agencies recommend reducing the server’s attack surface by:

• Configuring strong cryptography and authentication
• Running on strictly necessary features
• Protecting and monitoring access to and from the VPN

Releasing this document comes after threat actors, both financially motivated and state-supported, have focused lately on exploiting VPN vulnerabilities to achieve their goal.

The attack vector has attracted government-backed hackers, who leveraged vulnerabilities in VPN devices to penetrate networks belonging to governmental organizations and defense firms in various countries.

Earlier this year in April, cybersecurity company FireEye published a report about two state-backed groups, likely Chinese, that used a zero-day vulnerability in the Pulse Connect Secure (PCS) VPN appliance in attacks focused on U.S. defense industrial base (DIB) networks.

Around the same time, the NSA and CISA warned that hackers working for the Russian Foreign Intelligence Service (SVR) and known as APT29, Cozy Bear, and The Dukes had exploited and continued to exploit successfully bugs in Fortinet and Pulse Secure VPN devices for initial access onto a target network.

An advisory from the U.K. National Cyber Security Centre (NCSC) in May added appliances from Cisco and other network gear vendors to the list of products with vulnerabilities that SVR hackers exploited.

Ransomware gangs have also shown a massive interest in this type of network access vector. At least seven operations have exploited bugs in VPN solutions from Fortinet, Ivanti (Pulse), and SonicWall.