Cybersecurity researchers have observed the activity of a more advanced version of a fully-functional malware loader dubbed PureCrypter that has been actively distributing remote access Trojans (RATs) and information stealers since March 2021. Notorious malware samples delivered using PureCrypter include AsyncRAT, LokiBot, Remcos, Warzone RAT, NanoCore, Arkei Stealer, and RedLine Stealer. The updated features of the PureCrypter malware loader include new modules enriched with additional anti-analysis techniques, advanced encryption, and obfuscation enabling malware operators to evade detection.
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To access the dedicated Sigma rule, make sure to sign up or log into SOC Prime’s platform. This rule detects PureCrypter loader persistence reached by adding entries to the registry run key:
Suspicious PureCrypter Loader Persistence by Adding of Run Key to Registry (via registry_event)
The detection supports translations to 19 SIEM, EDR & XDR formats and is mapped to the MITRE ATT&CK® framework addressing the Persistence tactic with Boot or Logon Autostart Execution (T1547) as the main technique.
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The recent Zscaler cybersecurity research has provided insights into the evolution of PureCrypter loader, which has been in the cyber threat arena for over one year distributing multiple malware strains, including RATs and infostealers. The malware loader is actively being sold and promoted by its developer acting under the moniker “PureCoder”.
The infection chain contains two stages. In the first stage, a simple .NET PureCrypter downloader launches a more sophisticated second-stage module, which serves as the major payload and further injects the final malware, like a RAT or an info stealer as part of another process, for instance, MSBuild.
The PureCrypter loader author has enriched the new malware variant with the ability to send an infection status message via Discord and Telegram. Other PureCrypter features within an upgraded malware version include persistence, injection, and defense mechanisms along with more sophisticated encryption and obfuscation techniques to bypass detection. The advanced capability of PureCrypter injector to gain persistence at startup and the use of Google’s Protocol format makes it harder to detect by standard anti-virus software.
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