For years, it’s been an inconvenient truth within the cybersecurity industry that the network security devices sold to protect customers from spies and cybercriminals are, themselves, often the machines those intruders hack to gain access to their targets. Again and again, vulnerabilities in “perimeter” devices like firewalls and VPN appliances have become footholds for sophisticated hackers trying to break into the very systems those appliances were designed to safeguard.
Now one cybersecurity vendor is revealing how intensely—and for how long—it has battled with one group of hackers that have sought to exploit its products to their own advantage. For more than five years, the UK cybersecurity firm Sophos engaged in a cat-and-mouse game with one loosely connected team of adversaries who targeted its firewalls. The company went so far as to track down and monitor the specific devices on which the hackers were testing their intrusion techniques, surveil the hackers at work, and ultimately trace that focused, years-long exploitation effort to a single network of vulnerability researchers in Chengdu, China.
On Thursday, Sophos chronicled that half-decade-long war with those Chinese hackers in a report that details its escalating tit-for-tat. The company went as far as discreetly installing its own “implants” on the Chinese hackers’ Sophos devices to monitor and preempt their attempts at exploiting its firewalls. Sophos researchers even eventually obtained from the hackers’ test machines a specimen of “bootkit” malware designed to hide undetectably in the firewalls’ low-level code used to boot up the devices, a trick that has never been seen in the wild.
In the process, Sophos analysts identified a series of hacking campaigns that had started with indiscriminate mass exploitation of its products but eventually became more stealthy and targeted, hitting nuclear energy suppliers and regulators, military targets including a military hospital, telecoms, government and intelligence agencies, and the airport of one national capital. While most of the targets—which Sophos declined to identify in greater detail—were in South and Southeast Asia, a smaller number were in Europe, the Middle East, and the United States.
Sophos’ report ties those multiple hacking campaigns—with varying levels of confidence—to Chinese state-sponsored hacking groups including those known as APT41, APT31, and Volt Typhoon, the latter of which is a particularly aggressive team that has sought the ability to disrupt critical infrastructure in the US, including power grids. But the common thread throughout those efforts to hack Sophos’ devices, the company says, is not one of those previously identified hackers groups but instead a broader network of researchers that appears to have developed hacking techniques and supplied them to the Chinese government. Sophos’ analysts tie that exploit development to an academic institute and a contractor, both around Chengdu: Sichuan Silence Information Technology—a firm previously tied by Meta to Chinese state-run disinformation efforts—and the University of Electronic Science and Technology of China.
Sophos says it’s telling that story now not just to share a glimpse of China’s pipeline of hacking research and development, but also to break the cybersecurity industry’s awkward silence around the larger issue of vulnerabilities in security appliances serving as entry points for hackers. In just the past year, for instance, flaws in security products from other vendors including Avanti, Fortinet, Cisco, and Palo Alto have all been exploited in mass hacking or targeted intrusion campaigns. “This is becoming a bit of an open secret. People understand this is happening, but unfortunately everyone is zip,” says Sophos chief information security officer Ross McKerchar, miming pulling a zipper across his lips. “We’re taking a different approach, trying to be very transparent, to address this head-on and meet our adversary on the battlefield.”
From One Hacked Display to Waves of Mass Intrusion
As Sophos tells it, the company’s long-running battle with the Chinese hackers began in 2018 with a breach of Sophos itself. The company discovered a malware infection on a computer running a display screen in the Ahmedabad office of its India-based subsidiary Cyberoam. The malware had gotten Sophos’ attention due to its noisy scanning of the network. But when the company’s analysts looked more closely, they found that the hackers behind it had already compromised other machines on the Cyberoam network with a more sophisticated rootkit they identified as CloudSnooper. In retrospect, the company believes that initial intrusion was designed to gain intelligence about Sophos products that would enable follow-on attacks on its customers.
Then in the spring of 2020, Sophos began to learn about a broad campaign of indiscriminate infections of tens of thousands of firewalls around the world in an apparent attempt to install a trojan called Asnarök and create what it calls “operational relay boxes” or ORBs—essentially a botnet of compromised machines the hackers could use as launching points for other operations. The campaign was surprisingly well-resourced, exploiting multiple zero-day vulnerabilities the hackers appeared to have discovered in Sophos appliances. Only a bug in the malware’s cleanup attempts on a small fraction of the affected machines allowed Sophos to analyze the intrusions and begin to study the hackers targeting its products.
