SolarMarker Malware Activity

THE THREAT

eSentire has observed a recent and significant increase in SolarMarker infections delivered through drive-by download attacks. These attacks rely on social engineering techniques to persuade users to execute malware disguised as document templates. SolarMarker is a modular information-stealing malware; infections may result in the theft of sensitive data including user credentials.

eSentire is sharing details on these attacks, including indicators of compromise to increase awareness of this threat across our customers.

What we’re doing about it

• eSentire MDR for Endpoint detects this threat
• Known command and control addresses have been added to eSentire’s global block list
• eSentire security teams are tracking this threat for additional details and detection opportunities 

What you should do about it

• User awareness training. Warn users about the threat of drive-by download attacks. Threat actors will often employ industry-specific lures using industry terminology. Details of drive-by attacks employed by SolarMarker are included below
  • Always examine the file type/extension for unexpected Internet search results, e.g. documents with .exe or .msi extensions
  • Always examine the website before downloading files. Ask yourself whether the site matches the content you are attempting to download. For example, a bakery website hosting legal document templates is likely not authentic
  • Treat documents downloaded from unknown sources with suspicion
  • Be wary of web pages which require you to download your file from 3rd party sites
• Display file extensions for known file types
• Protect endpoints against malware
  • Ensure antivirus signatures are up-to-date
  • Use a Next-Gen AV (NGAV) or Endpoint Detection and Response (EDR) product to detect and contain threats

Additional information

What is SolarMarker?

SolarMarker is a modular information-stealing malware distributed through drive-by attacks. The malware is under active development and is highly evasive and difficult to detect.

How do the drive-by attacks work?

Victims are lured to malicious web pages via search engine results, often for document templates. For example, a user might search for a work-from-home policy guide and arrive on a SolarMarker delivery site. SolarMarker operators seed their websites with specific keywords which will flag in search results on popular search engines such as Google. Upon clicking on a search result, the user is presented with the option to download a PDF or Word version of the document they are seeking. Instead of a document, they are presented with a malicious executable (.exe) or Microsoft Installer (.msi) file.

Typical Infection Chain:

After successful execution, a generic decoy document is opened on the desktop:

What do the malicious documents look like?

When file extensions are hidden, SolarMarker appears in file explorer as a PDF (note the “type” field indicates it is an application).

When file extensions are shown, it is more apparent the file is not a PDF document:

A recent variant of this attack leverages Microsoft Installer files (.msi). These are not as well-disguised as documents, but they have still been successfully executed by victims.

SolarMarker .msi file with file extensions hidden:

SolarMarker .msi file with file extensions shown:

Observed Indicators of Compromise:

Payload Hosting

partnerinsignia[.]site
pdfdocdownloadspanel[.]site

SolarMarker Command-and-Control IP Addresses

146.70.24.173
167.88.15.115
185.236.203.153
185.244.213.64
23.108.57.102
23.29.115.175
37.120.237.251
37.120.247.199
45.42.201.248  

Files

03346A959C12EC00BF849A985A297ACE
0491CD2715E86E3D4B04F34A0DB03EF1
209A4C5F64BEDDCE266FA4CFBD61E7FF
34FB289E9FEE64CD7D4B588F0AF35A87
8693B9CFB8B4C466AE12CCDC2FEB46CE
C4772D76029004A5512EA6E2FF3BE39B
F4DD5F920BAC97CC0DE7AEA669E64DED

References:

[1] https://www.esentire.com/security-advisories/hackers-flood-the-web-with-100-000-malicious-pages-promising-professionals-free-business-forms-but-are-delivering-malware-reports-esentire
[2] https://blog.talosintelligence.com/2021/07/threat-spotlight-solarmarker.html
[3] https://blog.morphisec.com/new-jupyter-evasive-delivery-through-msi-installer
[4] https://squiblydoo.blog/2021/05/02/mars-deimos-solarmarker-jupyter-infostealer-part-1/