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The National Security Agency (NSA) and the Cybersecurity and Infrastructure Security Agency (CISA) have issued new guidance on selecting and improving the security of Virtual Private Networks (VPN) solutions.
VPN solutions allow remote workers to securely connect to business networks. Data traffic is routed through an encrypted virtual tunnel to prevent the interception of sensitive data and to block external attacks. VPNs are an attractive target for hackers, and vulnerabilities in VPN solutions have been targeted by several Advanced Persistent Threat (APT) groups. APT actors have been observed exploiting vulnerabilities in VPN solutions to remotely gain access to business networks, harvest credentials, remotely execute code on the VPN devices, hijack encrypted traffic sessions, and obtain sensitive data from the devices.
Several common vulnerabilities and exposures (CVEs) have been weaponized to gain access to the vulnerable devices, including Pulse Connect Secure SSL VPN (CVE-2019-11510), Fortinet FortiOS SSL VPN (CVE-2018-13379), and Palo Alto Networks PAN-OS (CVE_2020-2050). In some cases, threat actors have been observed exploiting vulnerabilities in VPN solutions within 24 hours of patches being made available.
Earlier this year, the NSA and CISA issued a warning that APT groups linked to the Russian Foreign Intelligence Service (SVR) had successfully exploited vulnerabilities in Fortinet and Pulse Secure VPN solutions to gain a foothold in the networks of U.S. companies and government agencies. Chinese nation state threat actors are believed to have exploited a Pulse Connect Secure vulnerability to gain access to the networks of the U.S. Defense Industrial Base Sector. Ransomware gangs have similarly been targeting vulnerabilities in VPNs to gain an initial foothold in networks to conduct double-extortion ransomware attacks.
The guidance document is intended to help organizations select secure VPN solutions from reputable vendors that comply with industry security standards who have a proven track record of remediating known vulnerabilities quickly. The guidance recommends only using VPN products that have been tested, validated and included in the National Information Assurance Partnership (NIAP) Product Compliant List. The guidance recommends against using Secure Sockets Layer/Transport Layer Security (SSL/TLS) VPNs, which use non-standard features to tunnel traffic via TLS as this creates additional risk exposure.
The guidance document also details best practices for hardening security and reducing the attack surface, such as configuring strong cryptography and authentication, only activating features that are strictly necessary, protecting and monitoring access to and from the VPN, implementing multi-factor authentication, and ensuring patches and updates are implemented promptly.