Feds Issue Updated Mitigations for Blocking Rhysida Ransomware Attacks
A joint cybersecurity advisory has been issued by the U.S. Cybersecurity and Infrastructure Security Agency (CISA), Federal Bureau of Investigation (FBI), and the Multi-State Information Sharing and Analysis Center (MS-ISAC) about Rhysida ransomware.
Rhysida ransomware is a ransomware-as-a-service (RaaS) operation that first emerged in May 2023. The group engages in double extortion tactics, involving data theft and encryption, with ransom payment required to obtain the keys to decrypt files and prevent the public release of stolen data. Researchers at Check Point identified significant similarities between Rhysida ransomware and Vice Society, one of the most prolific ransomware groups since 2021 that aggressively targeted the education and healthcare sectors.
In August 2023, the HHS’ Health Sector Cybersecurity Coordination Center (HC3) issued its own advisory about Rhysida ransomware following several attacks on the healthcare sector, including the attack on Prospect Medical Holdings, which affected 17 hospitals and 166 clinics across the United States. The latest cybersecurity advisory includes an update on the tactics, techniques, and procedures (TTPs) and Indicators of Compromise (IoCs) from malware analyses and recent incident response investigations to help network defenders and incident response teams detect and block attacks in progress.
Rhysida ransomware actors have been observed using a variety of techniques for gaining initial access to victims’ networks, including leveraging external-facing remote services such as virtual private networks (VPNs), commonly through the use of compromised credentials. These attacks have proven successful against organizations that have failed to implement multi-factor authentication for VPN connections. Rhysida ransomware actors have also exploited unpatched vulnerabilities, such as the Zerologon (CVE-2020-1472) vulnerability in Microsoft’s Netlogon Remote Protocol, and commonly use phishing emails. Once initial access has been achieved, the group often creates Remote Desktop Protocol (RDP) connections for lateral movement, establishes VPN access, and uses PowerShell and native network administration tools to perform operations, which helps them to evade detection by hiding their activity within normal Windows systems and network activities.
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The FBI, CISA, and the MS-ISAC suggest several mitigations for hardening security, including steps that can be taken to block the main attack vectors, restrict lateral movement and detect attacks in progress. These include enabling phishing-resistant multifactor authentication, especially for webmail, VPNs, and accounts that access critical systems; disabling command-line and scripting activities and permissions; restricting the use of PowerShell; enhancing PowerShell logging and logging within processes; restricting the use of RDP; and securing remote access through application controls.
Update: A free decryptor has been developed that could help victims of Rysida ransomware attacks recover their files for free.
