
Google Spots Tailored Backdoor Malware Aimed At SonicWall Appliances (therecord.media)
An anonymous reader quotes a report from The Record: Threat actors are stealing sensitive data from organizations by breaching end-of-life appliances made by cybersecurity company SonicWall. Incident responders from Google Threat Intelligence Group (GTIG) and Mandiant said on Wednesday that they have uncovered an ongoing campaign by an unidentified threat group that leverages credentials and one-time password (OTP) seeds stolen during previous intrusions -- allowing the hackers to regain access to organizations even after security updates are installed. [...]
The campaign is targeting fully patched end-of-life SonicWall Secure Mobile Access (SMA) 100 series appliances. Google explained that the malware the hackers are using removes log entries, making it difficult to figure out how they initially gained access to a system. Google said the campaign extends beyond the incidents they investigated directly and added that SonicWall has "confirmed reports of other impacted organizations." The company noted that SonicWall updated an advisory for a bug tracked as CVE-2024-38475 in light of Google's findings. "As an added security measure, we strongly advise customers to reset the OTP (One-Time Password) binding for all users. This step ensures that any potentially compromised or stale OTP secrets are invalidated, thereby mitigating unauthorized access risks," SonicWall said in the update to the advisory..
One novel aspect of the campaign is the use of a backdoor called OVERSTEP, which modifies the SonicWall appliance's boot process to maintain persistent access, steal sensitive credentials and conceal the malware's own components. Incident responders struggled to track other activities by the hackers because OVERSTEP allowed them to delete logs and largely cover their tracks. OVERSTEP is specifically designed for SonicWall SMA 100 series appliances, according to Google. In addition to CVE-2024-38475, Google and Mandiant experts floated several potential vulnerabilities the hackers may have used to gain initial access, including CVE-2021-20038, CVE-2024-38475, CVE-2021-20035, CVE-2021-20039 and, CVE-2025-32819. Beyond those, Google theorized that the hackers may have used an unknown zero-day vulnerability to deploy the malware on targeted SonicWall SMA appliances.
The campaign is targeting fully patched end-of-life SonicWall Secure Mobile Access (SMA) 100 series appliances. Google explained that the malware the hackers are using removes log entries, making it difficult to figure out how they initially gained access to a system. Google said the campaign extends beyond the incidents they investigated directly and added that SonicWall has "confirmed reports of other impacted organizations." The company noted that SonicWall updated an advisory for a bug tracked as CVE-2024-38475 in light of Google's findings. "As an added security measure, we strongly advise customers to reset the OTP (One-Time Password) binding for all users. This step ensures that any potentially compromised or stale OTP secrets are invalidated, thereby mitigating unauthorized access risks," SonicWall said in the update to the advisory..
One novel aspect of the campaign is the use of a backdoor called OVERSTEP, which modifies the SonicWall appliance's boot process to maintain persistent access, steal sensitive credentials and conceal the malware's own components. Incident responders struggled to track other activities by the hackers because OVERSTEP allowed them to delete logs and largely cover their tracks. OVERSTEP is specifically designed for SonicWall SMA 100 series appliances, according to Google. In addition to CVE-2024-38475, Google and Mandiant experts floated several potential vulnerabilities the hackers may have used to gain initial access, including CVE-2021-20038, CVE-2024-38475, CVE-2021-20035, CVE-2021-20039 and, CVE-2025-32819. Beyond those, Google theorized that the hackers may have used an unknown zero-day vulnerability to deploy the malware on targeted SonicWall SMA appliances.