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← RegistryDossier · 6 steps · 5 edges

Evil maid → sniff TPM unseal → decrypt BitLocker offline

Brief physical access to a TPM-only BitLocker laptop. Plug a logic analyser onto the LPC / SPI bus; capture the FVEK as the TPM unseals it at boot. Take the disk home, decrypt offline.

Filed by AD Knowledge Base
§ Kill-chainDrag · zoom · scroll

§ Context

Assumed environment: target laptop uses BitLocker with TPM-only protector (no PIN). Chassis can be opened in minutes; SPI / LPC bus accessible. Demonstrated repeatedly with ~10 USD logic analyzers.

§ Steps

  1. 01
    Exfil clear-text dataExfiltration
    T1041— Exfiltration Over C2 Channel
  2. 02
    Decrypt offline with captured keyCredential Access
    T1552— Unsecured Credentials
  3. 03
    Image the encrypted diskDiscovery
    T1083— File and Directory Discovery
  4. 04
    Attach logic analyzer to TPM busInitial Access
    IOT-UART-CONSOLE— UART Debug Console
  5. 05
    Open laptop chassisInitial Access
    FW-EVIL-MAID— Evil Maid Boot Tamper
  6. 06
    Trigger boot, capture FVEK on the wireCredential Access
    FW-TPM-RELAY— TPM Sniffing / Relay (BitLocker)

§ References

§ Frequently asked

What is the "Evil maid → sniff TPM unseal → decrypt BitLocker offline" attack path?
Brief physical access to a TPM-only BitLocker laptop. Plug a logic analyser onto the LPC / SPI bus; capture the FVEK as the TPM unseals it at boot. Take the disk home, decrypt offline. It chains 6 steps drawn from real-world offensive-security techniques.
What starting position does this attack require?
The first step is Exfil clear-text data (T1041) — a exfiltration primitive. Assumed environment: target laptop uses BitLocker with TPM-only protector (no PIN).
What is the final impact of this kill-chain?
The final step lands on Trigger boot, capture FVEK on the wire (FW-TPM-RELAY), which falls under Credential Access. From here, an operator typically pivots into post-exploitation or maintains persistence.
How can defenders detect or prevent this attack?
Detection and prevention vary per step. Refer to each linked MITRE ATT&CK entry under "References" — every technique on that page lists defensive controls, detection telemetry, and known threat-actor usage.

§ Related dossiers