Mass Router Hijack Targets End-of-Life ASUS Devices

 

The research team has found an extensive cyber-espionage campaign known as Operation WrtHug, which has quietly infiltrated tens of thousands of ASUS routers across the globe, which is a sign that everyday network infrastructure is becoming increasingly vulnerable. 

A seemingly routine home or small-office device that appears to be ordinary has been covertly repurposed to make up a sophisticated reconnaissance and relay network that has enabled threat actors to operate both anonymously and with great reach. There is a clear pattern in which consumer-grade routers are being strategically used for intelligence gathering, according to SecurityScorecard analysts, a trend that has been on the rise for several months now. 

Security specialists warn of the risk of such compromises becoming an ongoing trend in which outdated or poorly secured home routers are rapidly becoming valuable assets for hostile operators seeking persistence, cover, and distributed access to targeted environments that is no longer isolated incidents. In the last six months, investigators have determined that the operation’s reach has been much wider than they initially thought. 

As a result, over the past few months, nearly 50,000 unique IP addresses have responded to probing for compromised ASUS WRT routers. A chain of six unpatched vulnerabilities allowed the attackers to hijack these end of life or outdated devices and use them to develop a coordinated, globally distributed infrastructure by combining them with a series of unpatched vulnerabilities. 

Taiwan was attributed to the majority of routers infected, and significant clusters of routers were detected across Southeast Asia, Russia, Central Europe, and the United States. As a detail, the researchers noted that there were no infections within China, a detail that implies that the infection originates in China, but the available evidence is still insufficient for conclusive evidence to indicate a Chinese operator may be responsible. 

Moreover, the SecurityScorecard STRIKE team noticed that there were overlaps between the tactics and targeting patterns of Operation WrtHug, as well as the earlier AyySSHush campaign that was detected earlier by GreyNoise in May, suggesting that the campaign may be related to a much broader and well-organized effort to weaponize aging consumer networking products. 

A further analysis reveals that the intrusions seem to be connected to a coordinated effort to exploit a series of well-known vulnerabilities present in end-of-life ASUS WRT routers. This gives attackers the ability to perform full control over devices that remain unpatched, even after the end of the device's useful lifespan.

According to the investigators, each of the compromised routers has the same distinctive self-signed TLS certificate, which is supposed to expire a century after April 2022, suggesting the operation was carried out by the same set of toolset or deployment strategy. A report from SecurityScorecard states that nearly all of the services using this certificate are linked to ASUS's AiCloud platform. 

AiCloud is a proprietary feature that enables users to access their local storage over the internet and has become a convenient entry point for attackers who are leveraging n-day flaws to gain high-level access to hardware which is not supported. Researchers have noted parallels between this campaign and several China-linked ORBs and botnet ecosystems, despite its adherence to the classic profile of an Operational Relay Box network. 

According to the researchers, the attackers are relying on a cluster of vulnerabilities that include CVE-2023-41345, CVE-2023-41346, CVE-2023-41347, CVE-2023-41348, CVE-2023-39780, CVE-2024-12912, and CVE-2025-2492. The AyySSHush botnet is one of the routers that have been exploited in the past. 

A number of the infected IP addresses have been tagged with signs consistent with compromises made by both WrtHug and AyySSHush, which suggests that the two operations may be overlapping. However, researchers caution that any link between the two operations remains speculative and is solely based upon the exploitation of common vulnerabilities, rather than a confirmed coordination effort. According to security experts, the majority of infections that have been identified originate from Taiwan, with minor concentrations spreading throughout Southeast Asia, Russia, Central Europe, and the United States of America. 

A lot of the targeted ASUS models appear to be among the most vulnerable to the campaign-including the 4G-AC55U, 4G-AC860U, DSL-AC68U, GT-AC5300, GT-AX11000, RT-AC1200HP, RT-AC1300GPLUS, and RT-AC1300UHP-many of them no longer receiving updates and can no longer be supported. 

In the opinion of the STRIKE researchers, attackers are initiating their takeover by exploiting a high-impact command injection flaw along with several other known vulnerabilities to take control of the routers by converting them into operational relay boxes designed to conceal commands-and-control activities, so they can be integrated into these networks as a whole. 

It is important to note, however, that the researchers do not confirm the network's full operational role. Instead, they emphasize that the underlying vulnerabilities make these devices exceptionally valuable to hackers. It has been recommended that users immediately update their routers to address all six exploited flaws. 

Users of nonsupported routers, they warn, should either disable the remote access functions or retire them. Researchers noted that the attackers were not using undisclosed zero-day exploits, but rather a series of well-documented n-day vulnerabilities that are still unpatched on older ASUS WRT routers, providing a path to large-scale compromise that was possible without patching. 

Through this weakness, multiple forms of intrusion were possible, including OS command injection, which tricks a device into executing unauthorized system-level instructions, as well as remote code execution, which allows for complete authentication bypass as well. Using ASUS's AiCloud remote access service as a point of entry, SecurityScorecard's STRIKE team found that the threat actors were constantly exploiting ASUS's exposure to the internet, allowing them to gain a foothold on vulnerable devices. 

Once the routers were intruded into an extremely vast, global mesh network of hijacked systems once access had been secured. Research has identified over 50,000 unique IP addresses associated with compromised devices in the past six months alone. Based on analysis, analysts believe that the campaign's behavior resembles that of a covert network known as a Operational Relay Box, which involves repurposing everyday consumer devices as relays for espionage traffic, concealing the true source of espionage activity, and maintaining long-term persistence as a covert infrastructure model. 

As far as ORB-style operations are concerned, China-aligned threat groups are frequently associated with them, and this observation is reinforced by the geographical footprint of the infected devices. Security Scorecard found that about 30% to 50% of the compromised routers were based in Taiwan. Moreover, other concentrations have been observed in the United States, Russia, Southeast Asia and parts of Europe as well. 

There was also another distinctive technical signature that was shared by all of the infected routers, namely, a self-signed TLS certificate that had an unusually long valid period of 100 years, a sign that could be used by researchers to trace the campaign's infrastructure throughout multiple geographical locations. 

Together, these characteristics align closely with the pattern of cyber-espionage activities linked to China—including its choice of targets, methods of exploitation, design of operations, and geographic distribution. An important finding of the investigation is the geographical imbalance in which infected devices were detected, which scientists say is difficult to dismiss as coincidental by the researchers. 

According to analysts, one-third to one-half of all compromised routers identified in Operation WrtHug were traced back to IP addresses located in Taiwan - an overrepresentation that analysts argue is consistent with the long-standing intelligence priorities assigned to China-linked cyber operators, which is why this is an overrepresentation. 

A further striking feature of this study is that there have been no infections within mainland China, apart from a handful detected in Hong Kong, thereby highlighting the possibility of a deliberate targeting effort by the attackers. The attackers also seemed to be very interested in Southeast Asia, where the number of infected devices is substantially higher than the global average. 

In addition, researchers have noted striking tradecraft overlap between WrtHug and AyySSHush, another campaign outlined by GreyNoise earlier that aimed to use ASUS routers to conscript into a persistent botnet. The CVE-2023-39780 command injection vulnerability is used by both of these operations, raising the possibility that they could represent different phases of the same evolving campaign, separate efforts by the same threat actor, or parallel operations that are loosely coordinated.

It is still believed by analysts that WrtHug continues to be an independent campaign despite the fact that it carries the characteristics of a well-resourced adversary even though there is no conclusive evidence to prove it. It remains a fertile ground for such intrusions, despite the absence of conclusive evidence. Small office and home office routers are often installed only to be forgotten, especially as manufacturers discontinue support for them. 

It has become increasingly common for end-of-life devices to be updated automatically, but they still function as usual, and there seems to be little reason for users to replace them despite the mounting security risks. Despite the persistent gap, authorities have been increasingly concerned. The FBI released a public advisory in May calling for users of SOHO routers to disable remote management features as a minimum requirement in order to reduce the chances of compromise by retiring unsupported models. 

During the ongoing unfolding of Operation WrtHug, users' vigilance is becoming increasingly important as the security of global networks continues to become more dependent upon enterprise defenses, as well as the efforts of everyday users. As the findings indicate, households and small businesses need to abandon outdated hardware, implement timely patching, and limit their exposure to remote access services, which silently increase the attack surface of their networks. 

The experts stress that proactive maintenance - once considered optional - has now become a vital component of preventing consumer devices from being used as a tool in geopolitical cyber operations. With the rise of international espionage fueling neglected routers today, even basic security hygiene has become a matter of national importance.