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Introduction:
UEFI firmware is the new persistent playground for nation-state actors and advanced red teams – from BlackLotus to MosaicRegressor, bootkits are rewriting the rules of stealth. The open-source tool sl0ppy-UEFIScan has just received a massive v2.0 update, adding over a dozen advanced detection modules including SPI flash protection bypass checks, TPM 2.0 deep inspection, SMM exploit detection, and hardware root-of-trust validation.
Learning Objectives:
- Understand how to compile and run sl0ppy-UEFIScan to audit UEFI firmware for malicious capsules, rogue DXE drivers, and revoked Secure Boot keys.
- Learn to detect UEFI persistence mechanisms via NVRAM forensics and hidden EFI shell binaries.
- Master mitigation techniques against firmware rollback, virtualization escape, and side-channel attacks (Spectre/Meltdown) on both Linux and Windows systems.
You Should Know:
1. Compiling & Running sl0ppy-UEFIScan v2.0
The tool is not pre-compiled; you must clone and build it. Below are verified commands for Linux (Ubuntu/Debian) and Windows (with MSVC or MinGW).
Step‑by‑step guide:
Linux sudo apt install git build-essential cmake yara libyara-dev git clone https://github.com/Patrick-Hoogeveen/sl0ppy-UEFIScan.git hypothetical repo – replace with actual URL cd sl0ppy-UEFIScan mkdir build && cd build cmake .. && make sudo ./sl0ppy --help Windows (using WSL or MinGW) Install MSYS2 with mingw-w64, then: git clone <repo> cd sl0ppy-UEFIScan gcc -o sl0ppy.exe src/.c -lyara -luefidump adjust flags as needed
After compiling, run a full scan against a live UEFI system (requires root/admin):
sudo ./sl0ppy --scan all --report json --output uefi_audit.json
2. YARA Rule Expansion for Bootkit Detection
v2.0 includes new signatures for MosaicRegressor, FinFisher, and TrickBoot. To test custom YARA rules against your firmware dump, use:
Dump UEFI firmware via sysfs (Linux) sudo cat /sys/firmware/efi/efivars > firmware.dump caution: large file Or use flashrom sudo flashrom -r bios.bin Scan with YARA yara -r sl0ppy/rules/bootkit_rules.yara bios.bin
Windows PowerShell alternative:
Dump using RWEverything or Chipsec (requires admin) chipsec_util.py uefi dump Then run YARA from WSL
3. Firmware Capsule & BlackLotus Detection
BlackLotus abuses UEFI authenticated variables. sl0ppy‑UEFIScan validates capsule headers and checks for unsigned or malicious payloads.
Manual check using Linux efivarfs:
List all variables ls -la /sys/firmware/efi/efivars/ Examine suspicious GUIDs (e.g., 8be4df61-93ca-11d2-aa0d-00e098032b8c for BootOrder) hexdump -C /sys/firmware/efi/efivars/BootOrder-
Tool verification: sl0ppy will flag any capsule with mismatched signatures. To mitigate, enable Secure Boot and check `dbx` (UEFI revocation list) for BlackLotus hashes.
4. SPI Flash Protection & BIOS Write Bypass
Attackers often disable BIOS write protection to implant persistent backdoors. sl0ppy checks the status of SPI flash control registers.
Check protection on Linux:
sudo modprobe spi_chip cat /proc/mtd if MTD enabled sudo flashrom --wp-status
On Windows (using Chipsec):
cd chipsec python chipsec_main.py -m spi_linux or common.spi
If write protection is disabled, re‑enable via jumper or flashrom --wp-enable. For firmware hardening, set BIOS Admin password and lock SMM_BWP bit.
5. TPM 2.0 Deep Inspection & Attestation
The tool validates TPM NV indices, PCR banks, and attestation logs – critical for measured boot.
Query TPM on Linux:
sudo apt install tpm2-tools tpm2_pcrread sha256:0-23 tpm2_nvread 0x1c00002 common index for firmware version
On Windows (PowerShell as Admin):
Get-Tpm Get-TpmSupportedFeature Retrieve PCR logs Get-TpmEndorsementKeyInfo -HashAlgorithm Sha256
If PCRs mismatch, something altered the boot chain. Use `tpm2_pcrreset` after system verification.
- Secure Boot Key Validation (db, dbx, KEK, PK)
sl0ppy checks for revoked or malicious keys. Manual enumeration:
Linux:
efi-readvar -v db efi-readvar -v dbx efi-readvar -v KEK efi-readvar -v PK
Windows:
powershell "Get-SecureBootUEFI -1ame db"
To remove malicious keys, use `KeyTool.efi` or sbkeysync. Always keep `dbx` updated via fwupdmgr update.
7. SMM (System Management Mode) Exploit Detection (CVE-2023-20569)
SMM callout vulnerabilities can lead to SMM privilege escalation. sl0ppy scans for unsafe SMM communication buffers.
Check SMI handlers with UEFITool (manual):
Extract SMM drivers UEFIExtract bios.bin -o smm_drivers/ strings smm_drivers/ | grep -i "SmmCommunication"
Mitigation: Enable SMM protection via BIOS (SMM Lock, SMM_BWP), and use `msr-tools` to verify IA32_FEATURE_CONTROL.
sudo modprobe msr sudo rdmsr 0x3a check SMM lock bit
8. DXE Integrity & Malicious Driver Detection
Driver Execution Environment (DXE) drivers run before the OS – perfect for rootkits. sl0ppy computes hashes and compares against known‑bad lists.
Manual integrity check:
Extract DXE volumes UEFIExtract bios.bin --dxe-only Compute hashes sha256sum dxe_volume_.bin
Windows Sysinternals alternative: Use `autoruns` with “Hide Microsoft entries” to spot unsigned EFI drivers under HKLM\SYSTEM\CurrentControlSet\Control\UEFI.
To remove rogue DXEs, reflash a clean BIOS and set Intel Boot Guard to “verified boot”.
9. NVRAM Forensics & Persistence Mechanisms
Attackers write to NVRAM variables to survive reinstallations. sl0ppy dumps and inspects all variables.
Linux NVRAM extraction:
sudo cp -r /sys/firmware/efi/efivars /tmp/efivars_backup for var in /tmp/efivars_backup/; do echo "$(basename $var): $(hexdump -C $var)"; done
Detect anomalies: Look for `Boot` variables pointing to non‑existent devices, or variables with `EFI_VARIABLE_NON_VOLATILE` plus `EFI_VARIABLE_BOOTSERVICE_ACCESS` flags that shouldn’t exist.
10. Hardware Root of Trust & Anti‑Rollback Checks
sl0ppy validates Intel Boot Guard, AMD PSB, and ARM TrustZone status. It also checks if firmware rollback is possible.
Intel Boot Guard check:
Install intelmetool git clone https://github.com/corna/intelmetool cd intelmetool && make sudo ./intelmetool --bootguard shows verified boot status
Anti‑rollback mitigation: On supported platforms, enable “FW Rollback Protection” in BIOS. For Linux, use `fwupd` with `–disable-rollback` flag.
11. Virtualization Escape & Side‑Channel Mitigations
sl0ppy scans for VM escape primitives (QEMU, VMware, KVM) and checks Spectre/Meltdown protections.
Check KVM mitigations:
cat /sys/devices/system/cpu/vulnerabilities/ For Spectre v2, look for "mitigation: Full retpoline" For Meltdown, "Mitigation: PTI"
Enable hypervisor‑hardened settings:
<!-- QEMU: add -cpu host,+spec-ctrl,+ssbd,+1dpe1gb --> <!-- VMware: set monitor_control.enable_fullcpuid = "TRUE" -->
What Undercode Say:
- Key Takeaway 1: Sl0ppy‑UEFIScan v2.0 transforms open‑source firmware auditing from basic dumping to forensic‑grade detection – covering SMM exploits, TPM attestation, and hardware root of trust – making it essential for red teamers and defenders alike.
- Key Takeaway 2: Many enterprises still ignore UEFI hygiene; this tool reveals that BIOS write protection is often disabled, Secure Boot keys are stale, and NVRAM persists malicious variables. Regular scanning should become a compliance requirement.
Analysis (10 lines):
The update bridges a critical gap in low‑level security tooling. Until now, detecting BlackLotus or modifying `dbx` required expensive commercial tools or deep manual reversal. By open‑sourcing YARA rules for MosaicRegressor and adding SPI bypass checks, sl0ppy lowers the barrier for both blue teams (hunting persistent threats) and offensive practitioners (validating exploit chains). The inclusion of virtualisation escape detection is particularly timely given the rise of hypervisor rootkits. However, the lack of pre‑compiled binaries may deter Windows‑focused analysts; compiling against YARA and libuefidump can be finicky. The TPM 2.0 deep inspection stands out – most tools only check PCRs, but sl0ppy also validates NV indices and attestation logs, which attackers often corrupt. The anti‑rollback check is a wake‑up call: manufacturers that allow downgrades effectively nullify signed updates. Finally, the JSON reporting with actionable recommendations makes remediation trackable, a feature missing from many proof‑of‑concept scanners.
Prediction:
+1 Increased adoption of sl0ppy‑UEFIScan will force firmware vendors to publish SVN (Security Version Number) rollback counters and improve SMM lock defaults.
-1 Attackers will respond by developing polymorphic DXE drivers that evade YARA signatures, requiring ML‑based static analysis for UEFI.
+1 Regulatory bodies (NIST, CIS) will add UEFI scanning to their hardening benchmarks within 18 months.
-1 Organisations that ignore firmware audits will see a rise in “bootkit‑as‑a‑service” offerings, with persistence lasting over 365 days.
+1 The open‑source community will fork sl0ppy into a lightweight Windows GUI tool, making UEFI forensics accessible to SOC analysts.
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IT/Security Reporter URL:
Reported By: Patrick Hoogeveen – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
