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US-UK Gov Warning: SolarWinds Attackers Add Open-Source PenTest Tool to Arsenal

Agencies in the United States and the United Kingdom on Friday published a joint report providing more details on the activities of the Russian cyberspy group that is believed to be behind the attack on IT management company SolarWinds. The report reveals that the hackers started using the open-source adversary simulation framework Sliver after some of their operations were exposed.

The FBI, NSA, CISA and the UK’s NCSC say the Russian threat actor tracked as APT29 (aka the Dukes, Cozy Bear and Yttrium) was behind the SolarWinds attack, which resulted in hundreds of organizations having their systems breached through malicious updates served from compromised SolarWinds systems.

The agencies previously published several other reports on the activities of the group, which they say is controlled by a Russian intelligence agency named the Foreign Intelligence Service, or SVR.

The latest report shares more information on the tactics, techniques and procedures (TTPs) associated with the cyberspies, and also describes some of the changes made by the group in response to the previous reports.

Last year, the government agencies described APT29 operations targeting organizations in the US, UK and Canada that were involved in research and development of vaccines for the SARS‑CoV‑2 coronavirus. Those attacks involved pieces of malware tracked as WellMess and WellMail.

Apparently in response to the exposure of their operation targeting vaccine makers, the hackers started using an open-source framework named Sliver to maintain access to existing WellMess and WellMail victims.

Sliver is a legitimate tool developed by offensive security assessment firm Bishop Fox. It’s described as an adversary simulation and red team platform that can be used by organizations to perform security testing.

“As observed with the SolarWinds incidents, SVR operators often used separate command and control infrastructure for each victim of Sliver,” the agencies said.

The Snort and Yara rules included in the report focus on helping threat hunters detect Sliver. However, the agencies noted that since Sliver is a legitimate penetration testing tool, its presence does not necessarily indicate an attack by APT29.

The new cybersecurity advisory lists nearly a dozen vulnerabilities that have been exploited by APT29, and it reveals that the group has also started leveraging CVE-2021-21972. This is a critical vulnerability affecting VMware’s vCenter Server product. Organizations were warned in February that hackers had started scanning the internet for vulnerable servers just one day after VMware announced the availability of patches.

APT29 has apparently also started looking for Microsoft Exchange servers affected by the vulnerabilities that over the past two months have been exploited by many threat groups.

The report also shares some information on the impact of the attack on email security firm Mimecast, which was carried out through the SolarWinds breach.

Related: NSA: Russian Hackers Exploiting VPN Vulnerabilities - Patch Immediately

Related: FBI, CISA, ODNI Describe Response to SolarWinds Attack

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.