More SolarWinds Attack Details Emerge

As yet another piece of malware has been uncovered in the attack on SolarWinds network management system software, there still remain several missing elements needed to draw a complete picture of the massive cyberattacks against major US government agencies and corporations, including security vendor and incident response expert FireEye.

SolarWinds and CrowdStrike this week detailed a third malware tool — dubbed Sunspot — that was found in the attack on the software vendor. Sunspot is a custom program that inserted the so-called Sunburst backdoor into the software build environment of SolarWinds' Orion network management product. CrowdStrike, which analyzed Sunspot on behalf of SolarWinds, says the tool was carefully planted somehow by the attackers and kept hidden from SolarWinds developers with sophisticated tracking and camouflaging so it couldn't be detected.

"This is a purpose-built tool," says Adam Meyers, vice president of intelligence at CrowdStrike.

In a rare reversal of roles when it comes to nation-state attribution, the US intel community has publicly cited Russia as the perpetrator in the attacks, while security firms FireEye and CrowdStrike, which specialize in nation-state activity, have been unusually cautious in identifying a threat group or nation behind the attacks. Neither vendor will confirm whether it's Russia.

FireEye CEO Kevin Mandia last week noted during an Aspen Institute panel event that the attack group here "smells a lot different" despite similarities in its behavior to known nation-states. FireEye was the first to spot and report the attack on SolarWinds' software after discovering its own SolarWinds implementation had been targeted and that user credentials and its red-team tools had been stolen.

The attackers planted malware in legitimate updates to SolarWinds' Orion network management software that was sent to some 18,000 public and private sector customers of the software. According to US intelligence assessments, a very small number of those organizations actually were targeted and compromised.

"This is a pretty complex attack," CrowdStrike's Meyers says. "They've got absolutely immaculate opsec from what we've seen."

Case in point: The source code for Sunburst was embedded in Sunspot, he explains, but the attackers had done something he had never seen before. "We were excited to see source code for Sunburst but realized they had run it through a decompiler and laundered the code" so it was sanitized and left no fingerprints or other clues, he says.

The Sunspot implant also could be repurposed, he notes, and used with other source code by the attackers.

SolarWinds, which recently hired former CISA director Christopher Krebs and former Facebook security head Alex Stamos to assist in their breach recovery process, said the attackers appear to have first infiltrated the firm in September 2019 — likely for reconnaissance. According to a blog post by SolarWinds' newly appointed president and CEO Sudhakar Ramakrishna, the October 2019 version of Orion was modified such that the attackers could test their ability to insert code into its builds. The attackers began using Sunspot to insert Sunburst into Orion releases, starting on Feb. 20, 2020; the attackers later removed Sunburst in June of last year.

CrowdStrike's Meyers recommends that organizations "take a hard look" at their software build environments, especially if they are shipping code. "We see a lot of threat actors interested in targeting the supply chain," he says. "Awareness is key."

Aside from Sunspot and Sunburst, there's also Teardrop malware, a memory-based dropper that was used by the attackers to run a custom Cobalt Strike Beacon service for the attackers.

Turla Thread?
Kaspersky researchers, meanwhile, also found several commonalities between the Sunburst backdoor and a known backdoor called Kazuar, which was first detailed by Palo Alto Networks in 2017 and used for cyber-espionage campaigns by the Turla group. Turla is a Russian advanced persistent threat also known by the names of Snake, Venomous Bear, Uroburos, Group 88, and Waterbug, and is associated with cyber espionage.

Sunburst and Kazuar have some code overlap — specifically in their victim UID-generation algorithm, sleeping algorithm, and FNV-1a hash use, Kaspersky found. That doesn't prove they are from the same attack group, however, but the code could be somehow related or merely mimicked, according to Kaspersky.  

"We don't fully understand all of the different vectors or scope of this compromise," says Costin Raiu, director of Kaspersky's global research and analysis team. "But any bits of technically connected information can help."

Aside from the SolarWinds attack vector, there also are unsolved threads of additional initial attack vectors, including stolen credentials, according to CISA, which is looking into other attack methods in the campaign. There's also the December alert from the NSA warning of a VMware zero-day vulnerability that has some researchers, including Kaspersky's Raiu, wondering if it could be somehow related to the SolarWinds attacks, possibly as one of the other initial attack vectors outside of the SolarWinds software.

Either way, the supply chain attack via SolarWinds has the earmarks of nation-states, including Russia.

"I see SolarWinds [the attack] as a very natural element of an ecosystem that has existed" in cyber espionage for some time, says Gregory Rattray, co-founder and partner at Next Peak and former global CISO of JP Morgan Chase, who also served as White House cybersecurity director during the George W. Bush administration.

Rattray — who coined the now commonly used term for nation-state hackers, advanced persistent threat, or APT, while in the US Air Force — says the SolarWinds attack is just one of likely many similar supply chain compromises by stealthy and sophisticated groups.

"We're only seeing the tip of the iceberg. … There's a whole lot more of this."