ASUS Router Backdoors Affect 9,000 Devices, Persists After Firmware Updates

An anonymous reader quotes a report from SC Media: Thousands of ASUS routers have been compromised with malware-free backdoors in an ongoing campaign to potentially build a future botnet, GreyNoise reported Wednesday. The threat actors abuse security vulnerabilities and legitimate router features to establish persistent access without the use of malware, and these backdoors survive both reboots and firmware updates, making them difficult to remove.

The attacks, which researchers suspect are conducted by highly sophisticated threat actors, were first detected by GreyNoise's AI-powered Sift tool in mid-March and disclosed Thursday after coordination with government officials and industry partners. Sekoia.io also reported the compromise of thousands of ASUS routers in their investigation of a broader campaign, dubbed ViciousTrap, in which edge devices from other brands were also compromised to create a honeypot network. Sekoia.io found that the ASUS routers were not used to create honeypots, and that the threat actors gained SSH access using the same port, TCP/53282, identified by GreyNoise in their report. The backdoor campaign affects multiple ASUS router models, including the RT-AC3200, RT-AC3100, GT-AC2900, and Lyra Mini.

GreyNoise advises users to perform a full factory reset and manually reconfigure any potentially compromised device. To identify a breach, users should check for SSH access on TCP port 53282 and inspect the authorized_keys file for unauthorized entries.

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