A new threat which targets a range of routers and network-attached storage (NAS) devices is capable of knocking out infected devices by rendering them unusable. The malware, known as VPNFilter, is unlike most other IoT threats because it is capable of maintaining a persistent presence on an infected device, even after a reboot. VPNFilter has a range of capabilities including spying on traffic being routed through the device. Its creators appear to have a particular interest in SCADA industrial control systems, creating a module which specifically intercepts Modbus SCADA communications.
According to new research from Cisco Talos, activity surrounding the malware has stepped up in recent weeks and the attackers appear to be particularly interested in targets in Ukraine. While VPNFilter has spread widely, data from Symantec’s honeypots and sensors indicate that unlike other IoT threats such as Mirai, it does not appear to be scanning and indiscriminately attempting to infect every vulnerable device globally.
Q: What devices are known to be affected by VPNFilter?
A: To date, VPNFilter is known to be capable of infecting enterprise and small office/home office routers from Linksys, MikroTik, Netgear, and TP-Link, as well as QNAP network-attached storage (NAS) devices. These include:
- Linksys E1200
- Linksys E2500
- Linksys WRVS4400N
- Mikrotik RouterOS for Cloud Core Routers: Versions 1016, 1036, and 1072
- Netgear DGN2200
- Netgear R6400
- Netgear R7000
- Netgear R8000
- Netgear WNR1000
- Netgear WNR2000
- QNAP TS251
- QNAP TS439 Pro
- Other QNAP NAS devices running QTS software
- TP-Link R600VPN
Q: How does VPNFilter infect affected devices?
A: Most of the devices targeted are known to use default credentials and/or have known exploits, particularly for older versions. There is no indication at present that the exploit of zero-day vulnerabilities is involved in spreading the threat.
Q: What does VPNFilter do to an infected device?
A: VPNFilter is a multi-staged piece of malware. Stage 1 is installed first and is used to maintain a persistent presence on the infected device and will contact a command and control (C&C) server to download further modules.
Stage 2 contains the main payload and is capable of file collection, command execution, data exfiltration, and device management. It also has a destructive capability and can effectively “brick” the device if it receives a command from the attackers. It does this by overwriting a section of the device’s firmware and rebooting, rendering it unusable.
There are several known Stage 3 modules, which act as plugins for Stage 2. These include a packet sniffer for spying on traffic that is routed through the device, including theft of website credentials and monitoring of Modbus SCADA protocols. Another Stage 3 module allows Stage 2 to communicate using Tor.
Q: If I own an affected device, what should I do?
A: Users of affected devices are advised to reboot them immediately. If the device is infected with VPNFilter, rebooting will remove Stage 2 and any Stage 3 elements present on the device. This will (temporarily at least) remove the destructive component of VPNFilter. However, if infected, the continuing presence of Stage 1 means that Stages 2 and 3 can be reinstalled by the attackers.
You should then apply the latest available patches to affected devices and ensure that none use default credentials.
Q: If Stage 1 of VPNFilter persists even after a reboot, is there any way of removing it?
A: Yes. Performing a hard reset of the device, which restores factory settings, should wipe it clean and remove Stage 1. With most devices this can be done by pressing and holding a small reset switch when power cycling the device. However, bear in mind that any configuration details or credentials stored on the router should be backed up as these will be wiped by a hard reset.
Q: What do the attackers intend to do with VPNFilter’s destructive capability?
A: This is currently unknown. One possibility is using it for disruptive purposes, by bricking a large number of infected devices. Another possibility is more selective use to cover up evidence of attacks.
Q: Do Symantec/Norton products (Win/Mac/NMS) protect against this threat?
A: Symantec and Norton products detect the threat as Linux.VPNFilter.
Acknowledgement: Symantec wishes to thank Cisco Talos and the Cyber Threat Alliance for sharing information on this threat in advance of publication.
UPDATE: Netgear is advising customers that, in addition to applying the latest firmware updates and changing default passwords, users should ensure that remote management is turned off on their router. Remote management is turned off by default and can only be turned on using the router’s advanced settings. To turn it off, they should go to www.routerlogin.net in their browser and log in using their admin credentials. From there, they should click “Advanced” followed by “Remote Management”. If the check box for “Turn Remote Management On” is selected, clear it and click “Apply” to save changes.
UPDATE May 24, 2018: The FBI has announced that it has taken immediate action to disrupt the VPNFilter, securing a court order, authorizing it to seize a domain that is part of the malware’s C&C infrastructure.
Meanwhile, Linksys is advising customers to change administration passwords periodically and ensure software is regularly updated. If they believe they have been infected, a factory reset of their router is recommended. Full instructions can be found here.
MikroTik has said that it is highly certain that any of its devices infected by VPNFilter had the malware installed through a vulnerability in MikroTik RouterOS software, which was patched by MikroTik in March 2017. Upgrading RouterOS software deletes VPNFilter, any other third-party files and patches the vulnerability.
UPDATE May 25, 2018: QNAP has published a security advisory on VPNFilter. It contains guidance on how to use the company’s malware removal tool to remove any infections.
Credit: Symantec Security Response Team