LegionLoader DLL Sideloading via VMware mksSandbox Loading Fake libcrypto (via image_load)

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1574.001DLL
Persistence
- T1574.001DLL
Priv Esc
- T1574.001DLL
Defense Evasion
- T1574.001DLL
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects the legitimate VMware-signed mksSandbox.exe loading a libcrypto-1_1-x64.dll from outside the trusted VMware installation path, the DLL side-loading behavior used to stage LegionLoader after a fake CAPTCHA and Cloudflare Turnstile lure. Adversaries abuse a signed binary to execute a malicious OpenSSL impersonating DLL under a trusted process, making early detection critical for surfacing loader activity before browser credential and wallet theft.

Reporting behind it

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LegionLoader DLL Sideloading via VMware mksSandbox Loading Fake libcrypto (via image_load)

Pivot detection · T1574.001 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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