Researchers at Secureworks’ counter threat unit (CTU) were investigating the exploit of SolarWinds servers to deploy the Supernova web shell when collected evidence that linked the malicious activity to a China-linked cyber espionage group tracked as Spiral.
The attackers were observed exploiting the CVE-2020-10148 authentication bypass issue in the SolarWinds Orion API to remotely execute API commands.
Once the attackers have exploited the issue on a vulnerable server, they have deployed the Supernova web shell to disk using a PowerShell command.
“In late 2020, Secureworks® Counter Threat Unit™ (CTU) researchers observed a threat actor exploiting an internet-facing SolarWinds server to deploy the SUPERNOVA web shell. Additional analysis revealed similarities to intrusion activity identified on the same network earlier in 2020, suggesting the two intrusions are linked.” reads the analysis published by Secureworks. “CTU™ researchers attribute the intrusions to the SPIRAL threat group. Characteristics of the activity suggest the group is based in China.”
In December, shortly after the initial disclosure of the SolarWinds attack, several teams of researchers mentioned the existence of two second-stage payloads.
Security experts from Symantec, Palo Alto Networks, and Guidepoint reported that threat actors behind the SolarWinds attack were also planting a .NET web shell dubbed Supernova.
Researchers from Palo Alto Networks revealed that the malicious code is a tainted version of the legitimate .NET library “app_web_logoimagehandler.ashx.b6031896.dll” included in the SolarWinds Orion software.
According to SecureWorks, Supernova was used by threat actors for reconnaissance activities, to harvest credentials and exfiltrate data from the compromised systems.
Secureworks experts found similarities with previous intrusion activity, the analysis of an incident earlier in 2020 revealed that the threat actor initially gained access to the target network as early as 2018 by exploiting a vulnerable public-facing ManageEngine ServiceDesk server. The attacker leveraged the access to periodically harvest and exfiltrate domain credentials. In August 2020, the attackers used the same acces to harvest credentials from two servers, then used them to access files from Office 365-hosted SharePoint and OneDrive services.
The attackers used identical commands to dump the LSASS process via comsvcs.dll and used the same output file path, they also accessed the same servers, and used three compromised administrator accounts in both intrusions
“CTU researchers have associated Chinese threat groups with network intrusions involving the targeting of ManageEngine servers, maintenance of long-term access to periodically harvest credentials and exfiltrate data, and espionage or theft of intellectual property,” states the analysis. “Although SPIRAL activity shares these characteristics, the characteristics are insufficient for attributing SPIRAL’s country of origin. However, an additional characteristic of the August 2020 intrusion strengthens the Chinese connection.”
Anyway, the above intrusions are not linked to the SolarWinds supply chain attack. It is important to highlight that the intrusion investigated by SecureWorks was not caused by the exploitation of SolarWinds supply chain, but the attackers were able to add Supernova to Orion software
Supernova was not delivered through the SolarWinds updates.
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(SecurityAffairs – hacking, GootKit)