Playbook for VPN failed login attempts

Summary

Remote work options—or telework—require an enterprise virtual private network (VPN) solution to connect employees to an organization’s information technology (IT) network.

Technical Details

The following are cybersecurity considerations regarding telework.

• As organizations use VPNs for telework, more vulnerabilities are being found and targeted by malicious cyber actors.
• As VPNs are 24/7, organizations are less likely to keep them updated with the latest security updates and patches.
• Malicious cyber actors may increase phishing emails targeting teleworkers to steal their usernames and passwords.
• Organizations that do not use multi-factor authentication (MFA) for remote access are more susceptible to phishing attacks.
• Organizations may have a limited number of VPN connections, after which point no other employee can telework. With decreased availability, critical business operations may suffer, including IT security personnel’s ability to perform cybersecurity tasks.

Analysis

Analyse the instancesof failed login from the last 5 minutes, 1 hour, or 24 hours. The results can be sorted by the number of instances a given user attempted to log in.

Record the date and time of each login attempt, the message explaining the reason each authentication failed e.g. a mismatched password, and the source IP address.

Mitigations

• Update VPNs, network infrastructure devices, and devices being used to remote into work environments with the latest software patches and security configurations. See CISA Tips Understanding Patches and Securing Network Infrastructure Devices.
• Alert employees to an expected increase in phishing attempts. See CISA Tip Avoiding Social Engineering and Phishing Attacks.
• Ensure IT security personnel are prepared to ramp up the following remote access cybersecurity tasks: log review, attack detection, and incident response and recovery. Per the National Institute of Standards and Technology (NIST) Special Publication 800-46 v.2, Guide to Enterprise Telework, Remote Access, and Bring Your Own Device (BYOD) Security, these tasks should be documented in the configuration management policy.
• Implement MFA on all VPN connections to increase security. If MFA is not implemented, require teleworkers to use strong passwords. (See CISA Tips Choosing and Protecting Passwords and Supplementing Passwords for more information.)
• Ensure IT security personnel test VPN limitations to prepare for mass usage and, if possible, implement modifications—such as rate limiting—to prioritize users that will require higher bandwidths.
• Contact CISA to report incidents, phishing, malware, and other cybersecurity concerns.

References

References

NIST Special Publication 800-46 v.2, Guide to Enterprise Telework, Remote Acces…
CISA Cyber Essentials
CERT/CC: VPN – A Gateway for Vulnerabilities
US CERT
National Security Agency Cybersecurity Advisory: Mitigating Recent VPN Vulnerab…
CISA Insights: Risk Management for Novel Coronavirus (COVID-19)
Telework.gov Guidance

Blocking Brute Force Attack on GlobalProtect Portal Page
https://www.securityweek.com/two-popular-vpns-exposed-users-attacks-fake-updates

Revisions

March 13, 2020: Initial Version