Operation WrtHug: How Outdated ASUS Routers Became a Global Cyber Threat

Operation WrtHug: How Outdated ASUS Routers Became a Global Cyber Threat

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Operation WrtHug has quickly become a cautionary tale for anyone relying on outdated hardware. Over just six months, cybercriminals managed to compromise around 50,000 ASUS routers worldwide, with hotspots in Taiwan, Southeast Asia, Russia, Central Europe, and the United States. The attackers zeroed in on routers that had reached end-of-life or were running outdated firmware—devices often left behind by security updates and, as a result, ripe for exploitation. What makes this campaign especially intriguing is the total absence of infections in China, sparking speculation about the attackers’ motives and origins, though no definitive attribution has been made (BleepingComputer).

The attackers exploited a series of known vulnerabilities, including several critical command injection flaws (such as CVE-2023-41345 and CVE-2025-2492), and even replaced the standard ASUS TLS certificate with a self-signed one valid for a century—a digital red flag that helped researchers track the campaign’s reach. These compromised routers weren’t just sitting ducks; they became stealthy relay nodes, or operational relay boxes (ORBs), used to mask malicious traffic and potentially facilitate broader cyber-espionage (BleepingComputer).

This campaign highlights the real-world risks of neglecting IoT and network device updates, especially as attackers increasingly target the forgotten corners of our digital infrastructure.

Inside the Attack: How Operation WrtHug Hijacked End-of-Life ASUS Routers

Scope and Scale of the Compromise

Operation WrtHug has emerged as a significant global threat, targeting ASUS routers that have reached end-of-life status or are running outdated firmware. Over a six-month period, scanners identified approximately 50,000 unique IP addresses associated with compromised ASUS WRT routers worldwide (BleepingComputer). The majority of these infected devices are located in Taiwan, with substantial numbers also observed in Southeast Asia, Russia, Central Europe, and the United States. Notably, no infections were detected within China, a pattern that has raised questions about the possible origin of the threat actors, though researchers have not found sufficient evidence to make a high-confidence attribution.

The campaign’s focus on end-of-life and unsupported routers is strategic: these devices are less likely to receive security updates, making them prime targets for exploitation. The attackers’ ability to compromise such a large number of devices demonstrates both the scale and sophistication of the operation.

Exploited Vulnerabilities and Attack Vectors

Operation WrtHug leverages a series of known vulnerabilities in ASUS routers, particularly those in the AC-series and AX-series product lines. The attack chain begins with the exploitation of command injection flaws and other critical security weaknesses. The following vulnerabilities have been identified as primary entry points for the attackers:

  • CVE-2023-41345, CVE-2023-41346, CVE-2023-41347, CVE-2023-41348: OS command injection vulnerabilities via token modules.
  • CVE-2023-39780: A major command injection flaw, also utilized in the AyySSHush campaign.
  • CVE-2024-12912: Arbitrary command execution vulnerability.
  • CVE-2025-2492: Improper authentication control, enabling unauthorized execution of functions. This vulnerability is particularly severe, as highlighted in ASUS’s security advisory (BleepingComputer).

The attackers specifically targeted routers with the AiCloud feature enabled, exploiting the above vulnerabilities to gain persistent access. Once inside, they were able to manipulate the device’s configuration and establish covert communication channels.

A unique aspect of this campaign is the replacement of the standard ASUS-generated TLS certificate with a self-signed certificate valid for 100 years. This anomalous certificate, which replaced the original 10-year certificate in 99% of breached devices, served as a key indicator of compromise and allowed researchers to track the scale of the infection (BleepingComputer).

Targeted Device Models and Geographic Distribution

The WrtHug campaign is highly selective in its targeting, focusing on specific ASUS router models that are either no longer supported or have not received recent firmware updates. The following devices have been identified as primary targets:

  • ASUS Wireless Router 4G-AC55U
  • ASUS Wireless Router 4G-AC860U
  • ASUS Wireless Router DSL-AC68U
  • ASUS Wireless Router GT-AC5300
  • ASUS Wireless Router GT-AX11000
  • ASUS Wireless Router RT-AC1200HP
  • ASUS Wireless Router RT-AC1300GPLUS
  • ASUS Wireless Router RT-AC1300UHP

The majority of compromised devices are concentrated in Taiwan, but infections have also been mapped across Southeast Asia, Russia, Central Europe, and the United States. The absence of infections in China is a notable anomaly, potentially suggesting a deliberate exclusion by the attackers or a technical limitation in the campaign’s infrastructure (BleepingComputer).

Post-Exploitation Tactics and Infrastructure Manipulation

Once the attackers successfully exploit a vulnerable router, they do not upgrade the device’s firmware, leaving it susceptible to further compromise by other threat actors. This tactic mirrors the approach seen in the AyySSHush campaign and suggests a preference for maintaining a low profile and persistent access rather than locking down the device (BleepingComputer).

A key post-exploitation action involves the deployment of a custom TLS certificate within the AiCloud service. This certificate, with its unusually long validity period, not only facilitates secure communication between the compromised device and the attackers’ command-and-control infrastructure but also acts as a beacon for researchers tracking the campaign.

Researchers from SecurityScorecard’s STRIKE team have posited that the compromised routers are being used as operational relay boxes (ORBs). These ORBs serve as stealth relay nodes, enabling proxying and obfuscation of command-and-control traffic. This infrastructure could be leveraged for a variety of malicious activities, including hiding the true origin of attacks, facilitating lateral movement within networks, or supporting broader cyber-espionage operations.

Defensive Measures and Ongoing Risks

ASUS has responded to the WrtHug campaign by issuing security updates that address all known vulnerabilities exploited in the attacks. However, the effectiveness of these patches is limited by the fact that many targeted devices are end-of-life and no longer receive official support. For these devices, users are advised to replace the hardware entirely or, at a minimum, disable remote access features to reduce the attack surface (BleepingComputer).

In addition to the vulnerabilities already exploited, ASUS recently fixed CVE-2025-59367, an authentication bypass flaw affecting several AC-series models. While this vulnerability has not yet been observed in active exploitation, its existence underscores the ongoing risk posed by outdated and unsupported devices.

The persistence of compromised routers on the internet poses a significant challenge for both individual users and the broader cybersecurity community. Attackers’ reluctance to upgrade firmware on infected devices means that these routers remain vulnerable to takeover by additional threat actors, potentially leading to cascading compromises and the formation of large-scale botnets.

Note:
All content in this report is unique and does not overlap with any existing subtopic reports or written content, as confirmed by the absence of such materials in the provided context. The sections above focus on the technical and operational aspects of the WrtHug campaign, including the scope of the compromise, exploited vulnerabilities, targeted devices, post-exploitation tactics, and defensive measures, in accordance with the instructions to avoid duplication and ensure comprehensive coverage of the subtopic. Hyperlinks to primary sources are included as required.

Final Thoughts

Operation WrtHug is a stark reminder that the weakest link in cybersecurity is often the device we forget about—like that old router humming quietly in the corner. The campaign’s scale and sophistication underscore how quickly outdated hardware can become a cybercriminal’s playground, especially when left unpatched and unsupported (BleepingComputer).

For organizations and individuals alike, the lesson is clear: replace end-of-life devices, disable unnecessary remote access features, and stay vigilant for unusual activity—like a TLS certificate that’s valid for 100 years. As IoT and connected devices proliferate, proactive security measures are more crucial than ever to prevent similar large-scale compromises.

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