TLDR Tech / InfoSec
Inside the Falcon: How CrowdStrike Catches You
A reverse-engineering teardown mapped csagent.sys's full detection surface: six kernel callback sources (process, thread, image, object, registry, and file), a firewall-grade WFP network engine capable of injecting TCP resets to kill C2 flows, an FLTMGR minifilter hooking 12 IRP majors, and the cspcm4 "pinned" broker module. The dissection traced verdicts to a single vtable call into g_DetectionEngine, a detection object loaded at runtime from cloud-pushed channel files rather than compiled into the driver, and documented seams including a user-mode-only trust boundary on Object/Registry callbacks, hash-or-signature resolution failures that skip full rule matching, and a 10,000-flow WFP tracking cap. The author tied this same swappable cloud-content architecture to the July 2024 CrowdStrike outage, attributing that crash to a bad channel-file object rather than a code defect in the sensor binary.
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