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Security advisories — Sep 23, 2021

SolarMarker Malware Activity

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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

What you should do about it

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


SolarMarker Command-and-Control IP Addresses  




[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/

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