Cybersecurity researchers have detailed the inner workings of the cryptocurrency stealer malware that was distributed via 13 malicious NuGet packages as part of a supply chain attack targeting .NET developers.
The sophisticated typosquatting campaign, which was detailed by JFrog late last month, impersonated legitimate packages to execute PowerShell code designed to retrieve a follow-on binary from a hard-coded server.
The two-stage attack culminates in the deployment of a .NET-based persistent backdoor, called Impala Stealer, which is capable of gaining unauthorized access to users’ cryptocurrency accounts.
“The payload used a very rare obfuscation technique, called ‘.NET AoT compilation,’ which is a lot more stealthy than using ‘off the shelf’ obfuscators while still making the binary hard to reverse engineer,” JFrog told The Hacker News in a statement.
.NET AoT compilation is an optimization technique that allows apps to be ahead-of-time compiled to native code. Native AOT apps also have faster startup time and smaller memory footprints, and can run on a machine without .NET runtime installed.
“The bad actors used typosquatting techniques to deploy a custom malicious payload […] which targets the Exodus crypto wallet and leaks the victim’s credentials to cryptocurrency exchanges, by using code injection,” Shachar Menashe, senior director at JFrog Security Research, said.
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“Our investigation proves no open source software repository is completely trust-worthy, so safety measures should be taken at every step of the software development lifecycle to ensure the software supply chain remains secure.”
The findings come as Phylum unearthed a malicious npm package named mathjs-min that was uploaded to the repository on March 26, 2023, and found to harbor a credential stealer that grabs Discord passwords from the official app as well as web browsers like Google Chrome, Brave, and Opera.