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SolarWinds hackers are targeting Microsoft AD servers

The “passive and highly targeted" FoggyWeb backdoor has been around since at least April 2021

Nobelium, the hacking group responsible for last year’s cyber attack on SolarWinds, is now stealing data from Active Directory Federation Services (AD FS) servers.

That's according to Microsoft’s Threat Intelligence Center (MSTIC), which has issued a warning about Nobelium’s latest actions on its blog.

The Russian state-backed hacking group was found to be using a post-exploitation backdoor dubbed FoggyWeb in order to remotely exfiltrate sensitive data as well as maintain persistence on victims’ networks, warned MSTIC researcher Ramin Nafisi.

In order to steal the data, Nobelium hackers first gain admin privileges to AD FS servers by employing “multiple tactics to pursue credential theft”. Once they manage to compromise the server, they then deploy FoggyWeb “to remotely exfiltrate the configuration database of compromised AD FS servers, decrypted token-signing certificates and token-decryption certificates”, wrote Nafisi.

The “passive and highly targeted” FoggyWeb backdoor “has been observed in the wild as early as April 2021”, he added.

Microsoft stated that it had notified all customers believed to be targeted by Nobelium. However, it didn’t rule out that some organisations might still be at risk. It recommends that potential victims audit their on-premises and cloud infrastructure, “remove user and app access”, strengthen their passwords, as well as “use a hardware security module (HSM) in securing AD FS servers to prevent the exfiltration of secrets by FoggyWeb”.

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The tech giant also advised organisations to “harden and secure AD FS deployments” by taking additional measures, including limiting on-network access via host firewall and requiring all cloud admins to use multi-factor authentication.

The warning comes three months after Nobelium was found to have engaged in “password spray and brute-force attacks” on Microsoft’s customers, with around 10% of the targets being based in the UK.

The hackers implanted “information-stealing malware” on a device belonging to a Microsoft customer support agent, through which they obtained “basic account information for a small number of [Microsoft’s] customers”, according to the tech giant.

Prior to this, Nobelium launched a wave of attacks on more than 150 government agencies, think tanks, consultants, and NGOs from 24 countries, targeting an estimated 3,000 email accounts.

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