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Zyxel Warns Customers of Attacks on Security Appliances

Networking device manufacturer Zyxel has issued an alert to warn customers of attacks targeting a subset of security appliances that have remote management or SSL VPN enabled.

Networking device manufacturer Zyxel has issued an alert to warn customers of attacks targeting a subset of security appliances that have remote management or SSL VPN enabled.

In the letter sent to customers, a copy of which security researcher JAMESWT shared on Twitter, the company says that a sophisticated threat actor is targeting USG/ZyWALL, USG FLEX, ATP, and VPN series devices running on-premises ZLD firmware.

The company said that the threat actor attempts to access the target devices through WAN and, if they succeed, they then bypass authentication to establish SSL VPN channels.

To ensure their activity can continue unhindered, the adversary uses a series of user accounts that include “zyxel_silvpn,” “zyxel_ts,” or “zyxel_vpn_test,” which are used to manipulate the device’s configuration.

[ Related: Backdoors Found in Zyxel CloudCNM SecuManager Software ]

Zyxel says that the company has launched an investigation into the attacks and that it is working to resolve the issue.

“Based on our investigation so far, we believe maintaining a proper security policy for remote access is currently the most effective way to reduce the attack surface,” the company said.

The company did not say whether the attackers are targeting known or new vulnerabilities in the enterprise appliances.

In January, the company announced a patch for a hardcoded credentials vulnerability in these devices and other models, which threat actors started targeting almost immediately in attacks.  

To stay protected in the work-from-home era, Zyxel recommends keeping connected to the Internet only those applications and services that are mandatory for remote access, as well as configuring the perimeter firewall based on the least privilege principle and keeping devices patched at all times.

Related: Many Backdoors Found in Zyxel CloudCNM SecuManager Software

Related: Over 20 Zyxel Firewalls Impacted by Recent Zero-Day Vulnerability

Related: Zyxel Patches Zero-Day Vulnerability in Network Storage Products

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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