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Ryuk Continues to Dominate Ransomware Response Cases

Analysis reveals how Ryuk's operators are changing their techniques and using new means to break in.

Ryuk has dominated the ransomware threat landscape for the fourth consecutive quarter, Cisco Talos researchers report in an analysis of incident response trends. Its operators are changing strategy, posing greater risk to organizations whose response efforts are impeded by COVID-19. 

Ransomware continued to make up the majority of threats observed by the Cisco Talos Incident Response (CTIR) team, which today published its analysis of summer incident response trends. Ryuk has been a top ransomware threat to customers over the last year, says Sean Mason, general manager of CTIR, though the team also sees other families, including Phobos and Maze.

Over the past few quarters, Ryuk has evolved in ways that indicate its operators are shifting their tactics, Mason explains, pointing to an example: "We do see an emerging trend in Ryuk, where it is not necessarily preceded by a commodity Trojan infection, which may allow it to go undetected for some time and lead to the increased infections we are seeing," he says.

CTIR is seeing fewer incidents in which Emotet and TrickBot serve as the initial dropper for Ryuk ransomware, one of the reasons why there are fewer attacks using commodity Trojans overall. Its operators have shifted to living-off-the-land tools, which can help them bypass security tools, stay quiet, and give them a longer time frame to achieve their goals. 

"By limiting the noise and doing their best to blend in, they may be able to avoid detection and buy more time in which to traverse the network and accomplish their objectives," Mason notes. 

The ransomware has evolved in other ways as well. Ryuk used encoded PowerShell commands to download the initial payload, disable antivirus and security tools, stop backups, and scan the network to provide a list of online vs. offline hosts. Its operators are using more Windows Management Instrumentation (WMI) and BitsAdmin to deploy Ryuk in addition to PsExec. CTIR saw ransomware attackers exfiltrating sensitive data to use as leverage to force victims to pay ransom, continuing a trend that started in 2019, .

"As actors have continued to find ransomware a lucrative business model, and with the additional threat of extortion of blackmail, actors have shown a willingness to continually update their malware by adding new modules for increased lateral movement and data exfiltration," Mason explains.

CTIR reports a range of verticals were hit over the past quarter: energy and utilities, financial services, government, healthcare, industrial distribution, manufacturing, retail, technology, telecommunications, and transportation. Healthcare and tech were hit hardest, replacing financial services and government, which were the top targets in the previous quarter.

How Ryuk Breaks In
Phishing remained the top attack vector in engagements where the initial entry point could be identified, researchers explain, noting this was difficult due to shortfalls in logging. Even so, CTIR saw several cases in which attackers brute-forced a target's remote desktop services. It's difficult to say what's contributing to this shift; however, Mason hypothesizes it could be partly due to the rise in remote workers linked to COVID-19, which has expanded the attack surface.

"Additionally, we saw an uptick in Phobos ransomware attacks, [which] typically leverage compromised RDS connections as an initial vector," he says. "Despite these upticks, phishing still remains the top infection vector that we've seen, for the fourth quarter in a row."

While attackers have been using coronavirus-related lures in phishing campaigns, CTIR did not see any engagements that leveraged COVID-19. They did notice the pandemic is affecting organizations, especially those in the healthcare space, in their ability to respond to attacks. Pre-COVID-19 incident response planning didn't account for both a pandemic and a cyberattack, and coronavirus has limited the travel, staff, and budget needed to handle attacks. 

"From an overarching perspective, no planning had taken into account both a pandemic and cybersecurity incident happening in parallel," Mason says. Factors such as bandwidth limitations and people tasked with response being exposed to the virus and forced into quarantine are rare but have affected organizations' ability to handle these kinds of attacks.

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