Hacker Group Infrastructure That Uses Weaponized MS Word Docs Uncovered

Gamaredon, also known as Primitive Bear, Actinium, or Shuckworm, is a Russian Advanced Persistent Threat (APT) group active since at least 2013.

It is a very aggressive threat group that employs prolonged attacks that are highly disguised and particularly aggressive.

The gang distributes malware disguised in MS Word documents via spear phishing and social engineering attacks.

Silent Push investigates the Gamaredon Group’s rapid flux operation. Over 300 new apex domain IOCs were found in just one Gamaredon domain.

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Using Weaponized MS Word Documents

When the document is accessed, and the user has satisfied one or more requirements – such as geographic location, device type, and system specification – before delivery, the payload is hosted on a template downloaded from an attacker-controlled site.

“A large amount of Gamaredon subdomains used in spear phishing attacks are linked to the TLD .ru, registered via REGRU-RU, and contain the number 71”, according to the information shared with Cyber Security News.

Gamaredon employs infinite IP addresses to avoid discovery and uses wildcard A records instead of specified subdomains in fast fluxing.

APT groups utilize fast fluxing to avoid standard threat detection methods that rely on threat feeds providing entire domain names, including subdomains.

Several websites have reported recent efforts by Gamaredon to inject malware from the following URLs using an MS Word template:

• http://encyclopedia83.samiseto[.]ru/HOME-PC/registry/amiable/prick/sorry[.]83glf
• http://relation46.samiseto[.]ru/DESKTOP-UVHG99D/percy[.]46rra

“We discovered 98 A records associated with *samiseto[.]ru, that were used in constant rotation”, researchers said.

Additional research showed that IP addresses are only utilized for up to 4 days before being replaced by new IPs (together with new subdomains), which helps threat actors avoid detection and renders the majority of isolated IOCs useless upon discovery.

In the past, there have been documented attacks against Western government institutions across the US, the Indian Subcontinent, and more recently in Ukraine.

Recommendation

Organizations should implement countermeasures that track the underlying infrastructure that backs up attacks, such as apex domains, ASNs, registrars, authoritative nameservers, etc., rather than relying on lists of isolated IOCs.

They should also apply correlative datasets that allow security teams to identify patterns in attacker behavior, such as ASN and IP diversity data, naming conventions, etc.

Organizations must recognize and block apex domains regardless of the subdomain to protect themselves from quick flux TTPs.

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