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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
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
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:
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