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LockBit Ransomware Gang, Cybercriminals Exploiting 'Citrix Bleed' Vulnerability CISA Warns

Federal cyber officials issued a warning this week, revealing that both nation-state hackers and cybercriminal groups are capitalizing on a vulnerability within Citrix products, a threat that has left government agencies and major corporations exposed to potential attacks. Termed the 'Citrix Bleed' bug, this vulnerability has been a cause for concern for several weeks, as experts sounded the alarm about entities leaving their Citrix appliances unprotected, effectively leaving the door wide open to malicious actors.

In response to this escalating danger, the Cybersecurity and Infrastructure Security Agency (CISA), in collaboration with the FBI and cybersecurity authorities in Australia, released an advisory regarding the exploitation of CVE-2023-4966. This vulnerability affects NetScaler ADC and NetScaler Gateway appliances, widely employed by companies for network traffic management.

During a press call, Eric Goldstein, CISA's Executive Assistant Director for Cybersecurity, confirmed the disconcerting reality that both nation-state hackers and cybercriminal outfits, including the LockBit ransomware gang, are actively exploiting this bug. While thousands of organizations remain susceptible, over 300 entities have already received warnings through CISA's Ransomware Vulnerability Warning Program.

One prominent target that fell victim to this vulnerability was Boeing, whose parts and distribution business suffered an attack by LockBit earlier this month. In their advisory, CISA and the FBI disclosed that Boeing had voluntarily shared information regarding the attack. This incident confirmed that hackers, utilizing the latest LockBit 3.0 ransomware, exploited CVE-2023-4966 to gain initial access to Boeing Distribution Inc. Other organizations have also reported experiencing similar threats.

The advisory details the Citrix Bleed vulnerability leveraged by LockBit 3.0 affiliates, enabling threat actors to bypass password requirements and multifactor authentication (MFA). This vulnerability allows for session hijacking of legitimate user sessions on Citrix NetScaler web application delivery control (ADC) and Gateway appliances. As a result, malicious actors acquire elevated privileges, enabling them to harvest credentials, move laterally within the network, and access sensitive data and resources.

To combat these threats, the agencies urgently recommended isolating NetScaler ADC and Gateway appliances and promptly applying necessary software updates. The attacks associated with Citrix Bleed initially emerged in August, despite a security bulletin from Citrix in October that rated the bug at 9.4 out of 10 on the CVSS severity scale. Shockingly, ShadowServer data revealed that numerous instances remained vulnerable to the issue as of November 2, with nearly 2,000 in North America alone. CISA had mandated that all federal civilian agencies patch the vulnerability by November 8.

This growing danger has prompted heightened concern, with cybersecurity experts reporting that at least two ransomware gangs are attempting to exploit the vulnerability. The ease with which Citrix Bleed can be exploited has led experts to anticipate widespread exploitation, posing a grave threat to both private and public networks.

Once inside the compromised systems, LockBit actors were observed employing remote management and monitoring tools such as AnyDesk and Splashtop to extend their access and control. In response to these developments, CISA and the FBI have laid out a comprehensive playbook for organizations to investigate potential compromises and to take steps to mitigate threats.

The senior FBI official addressed the mounting concerns surrounding the U.S. government's response to LockBit's relentless string of attacks, emphasizing a multifaceted approach that encompasses enforcement actions, infrastructure takedowns, and seizures to raise the cost for ransomware actors engaging in criminal activities. The recent cybersecurity breach exploiting the Citrix Bleed vulnerability has prompted experts to voice their concerns and provide valuable insights on the unfolding situation.

Almog Apirion, CEO & Co-Founder of Cyolo, emphasized the escalating risks associated with outsourcing sensitive data, particularly as third-party attacks continue to target larger corporations' networks. He expressed apprehensions about the potential long-term consequences of the breach, including "identity theft, financial fraud, and further organizational damage." Apirion called for proactive measures, urging organizations to treat all third-party entities as high-risk and implement security protocols like "Multi-Factor Authentication (MFA)" to gain control and visibility over their systems.

Sean McNee, VP of Research and Data at DomainTools, an expert in domain intelligence, commended the Canadian government's swift response to the breach, applauding their "transparency, decisiveness, and speed" in reporting the incident and supporting affected citizens. McNee offered practical advice to those impacted, recommending actions such as "replace any documentation that the government advises, monitor your credit reports for any suspicious or fraudulent activities, ensure you have strong and unique passwords to critical online accounts, and enable multi-factor authentication when possible." He also emphasized the importance of reviewing security and account recovery questions due to the potential exposure of such information in the breach.

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