The adversary is changing its tools to avoid detection while attacking the vulnerabilities governments issue warnings about.
The Russian hacker group behind the historic SolarWinds intrusion that affected nine federal agencies keeps adjusting their tactics based on government advisories, U.S. and U.K. cybersecurity-focused agencies warn.
A joint advisory issued Friday by the U.K.’s National Cyber Security Centre, the Cybersecurity and Infrastructure Security Agency, the National Security Agency and the FBI specifically said Russia’s Foreign Intelligence Service (SVR) changed its behavior after the release of a July 2020 advisory on the group, also known as APT29. The U.S. and U.K. attributed the SolarWinds campaign to the Russian threat actor in April. The July advisory warned they were also targeting COVID-19 vaccine development.
“SVR cyber operators appear to have reacted to this report by changing their [tactics, techniques and procedures] in an attempt to avoid further detection and remediation efforts by network defenders,” reads the new advisory. “These changes included the deployment of the open-source tool Sliver in an attempt to maintain their accesses.”
Sliver is a “red team” tool, meaning it is used by legitimate actors to test an entity’s network defenses. CISA listed it in conjunction with Cobalt Strike—a similar tool that can provide adversaries with command and control functionality—in a fact sheet the agency published Friday summarizing recent activity they associate with the Russian threat group and the SolarWinds event.
The hackers gain initial access using a variety of malware—including WellMess and WellMail to target vaccine development organizations—described in the advisory. They then use tools like Sliver, in addition to credential theft, to retain their presence. And they use painstaking measures to hide their activity.
“The use of the Sliver framework was likely an attempt to ensure access to a number of the existing WellMess and WellMail victims was maintained following the exposure of those capabilities,” the agencies advised. “As observed with the SolarWinds incidents, SVR operators often used separate command and control infrastructure for each victim of Sliver.”
In general, the agencies said the adversary is leveraging the government advisories to exploit vulnerabilities—including those Microsoft has associated with Chinese hackers—and encouraged organizations to more quickly update their systems.
“The group has also been observed making use of numerous vulnerabilities, most recently the widely reported Microsoft Exchange vulnerability,” according to the joint advisory. “The group frequently uses publicly available exploits to conduct widespread scanning and exploitation against vulnerable systems. The group seeks to take full advantage of a variety of exploits when publicised. The group will look to rapidly exploit recently released public vulnerabilities which are likely to enable initial access to their targets.”
Officials have said both the Microsoft Exchange vulnerabilities and Microsoft Office 365 compromises they connect to the Russian actors are applicable to on-premises instances. Friday’s advisory encouraged organizations to use the full extent of available auditing mechanisms, an issue that has become a hot topic given that Microsoft has generally charged extra for full logging capabilities.
“Organisations should ensure sufficient logging (both cloud and on premises) is enabled and stored for a suitable amount of time, to identify compromised accounts, exfiltrated material and actor infrastructure,” the advisory reads. “As part of Microsoft's 'Advanced Auditing' functionality, Microsoft have introduced a new mailbox auditing action called 'MailItemsAccessed' which helps with investigating the compromise of email accounts. This is part of Exchange mailbox auditing and is enabled by default for users that are assigned an Office 365 or Microsoft 365 E5 license or for organisations with a Microsoft 365 E5 compliance add-on subscription.”
On the top of the advisory’s list of mitigations are familiar instructions: Organizations should patch faster and implement cybersecurity basics.
“Despite the complexity of supply chain attacks, following basic cyber security principles will make it harder for even sophisticated actors to compromise target networks,” the agencies said. “Implementing good network security controls and effectively managing user privileges organisations will help prevent lateral movement between hosts. This will help limit the effectiveness of even complex attacks.”