--- name: performing-firmware-malware-analysis-d2dde54e7094 description: 'Analyzes firmware images for embedded malware, backdoors, and unauthorized modifications in routers, IoT devices, UEFI/BIOS, and embedded systems, covering firmware extraction, filesystem analysis, binary reverse engineering, and bootkit detection. Use for firmware security analysis, IoT malware investigation, UEFI rootkit detection, or embedded device compromise assessment. ' domain: cybersecurity subdomain: malware-analysis tags: - malware - firmware - IoT - UEFI - embedded-security version: 1.0.0 author: mahipal license: Apache-2.0 nist_csf: - DE.AE-02 - RS.AN-03 - ID.RA-01 - DE.CM-01 mitre_attack: - T1027 - T1055 - T1140 - T1497 - T1505.003 --- # Performing Firmware Malware Analysis ## When to Use - A compromised IoT device or router needs firmware analysis to identify implanted backdoors - Investigating UEFI/BIOS rootkits that persist across OS reinstallations - Analyzing firmware updates for supply chain compromise or malicious modifications - Extracting and examining embedded Linux filesystems from IoT device firmware images - Verifying firmware integrity after a suspected hardware or firmware-level compromise **Do not use** for standard operating system malware; use PE/ELF analysis tools for OS-level malware on conventional systems. ## Prerequisites - binwalk installed for firmware image analysis and extraction (`pip install binwalk`) - Ghidra with ARM/MIPS architecture support for embedded binary reverse engineering - UEFI Tool (UEFITool) for UEFI firmware parsing and analysis - Firmware Analysis Toolkit (FAT) or EMBA for automated firmware analysis - QEMU for emulating extracted firmware filesystems - Cross-compilation toolchains for ARM, MIPS, and other embedded architectures ## Workflow ### Step 1: Extract and Identify Firmware Components Analyze the firmware image structure and extract filesystems: ```bash # Identify embedded filesystems and compressed data binwalk firmware.bin # Extract all identified components binwalk -e firmware.bin # Recursive extraction with signature scanning binwalk -eM firmware.bin # Output typically includes: # - Bootloader (U-Boot, GRUB, custom) # - Kernel image (Linux, RTOS) # - Root filesystem (SquashFS, JFFS2, CramFS, ext4) # - Configuration data # - Digital signatures or checksums # Entropy analysis to find encrypted or compressed regions binwalk -E firmware.bin # Identify specific filesystem types file _firmware.bin.extracted/* # For SquashFS filesystems unsquashfs _firmware.bin.extracted/squashfs-root.img ls squashfs-root/ ``` ### Step 2: Analyze the Extracted Filesystem Search for malicious modifications in the firmware filesystem: ```bash # Directory structure analysis find squashfs-root/ -type f | head -50 # Search for suspicious files find squashfs-root/ -name "*.sh" -exec ls -la {} \; find squashfs-root/ -perm -4000 -type f # SUID binaries find squashfs-root/ -name "*.so" -newer squashfs-root/bin/busybox # Modified libraries # Check startup scripts for backdoors cat squashfs-root/etc/init.d/rcS cat squashfs-root/etc/inittab ls -la squashfs-root/etc/rc.d/ # Search for hardcoded credentials grep -rn "password\|passwd\|secret\|key\|token" squashfs-root/etc/ 2>/dev/null grep -rn "root:" squashfs-root/etc/shadow 2>/dev/null # Check for unauthorized SSH keys find squashfs-root/ -name "authorized_keys" -exec cat {} \; # Network configuration backdoors cat squashfs-root/etc/hosts grep -rn "iptables\|nc\|netcat\|ncat" squashfs-root/etc/ squashfs-root/usr/bin/ # Check for reverse shells in cron find squashfs-root/ -name "crontab" -o -name "cron*" | xargs cat 2>/dev/null # Identify all ELF binaries for analysis find squashfs-root/ -type f -exec file {} \; | grep ELF ``` ### Step 3: Reverse Engineer Suspicious Binaries Analyze extracted binaries that may be backdoors: ```bash # Identify architecture and format file squashfs-root/usr/bin/suspicious_binary # Extract strings for IOC discovery strings squashfs-root/usr/bin/suspicious_binary | grep -iE "http|ip|port|shell|connect|exec" # Cross-reference against known firmware binaries # Compare SHA-256 hashes with known-good firmware sha256sum squashfs-root/usr/bin/* > current_hashes.txt # diff against baseline: diff baseline_hashes.txt current_hashes.txt # Import into Ghidra for disassembly (select correct architecture) # ARM: ARM/AARCH64 (Little Endian for most IoT devices) # MIPS: MIPS/MIPS64 (Big or Little Endian depending on device) # x86: For UEFI modules # Analyze with radare2 for quick triage r2 -A squashfs-root/usr/bin/suspicious_binary # Commands: afl (function list), pdf @main (disassemble main), iz (strings) ``` ### Step 4: UEFI/BIOS Firmware Analysis Analyze system firmware for bootkits and implants: ```bash # Extract UEFI firmware volumes with UEFITool # GUI: UEFITool -> File -> Open -> Select firmware.rom # CLI: UEFIExtract firmware.rom # Analyze UEFI firmware with chipsec (requires hardware access) python chipsec_main.py -m common.bios_wp # BIOS write protection python chipsec_main.py -m common.spi_lock # SPI flash lock python chipsec_main.py -m common.secureboot # Secure Boot status python chipsec_main.py -m common.uefi.s3bootscript # S3 resume script # Dump UEFI firmware from live system python chipsec_util.py spi dump firmware_dump.rom # Compare with known-good firmware sha256sum firmware_dump.rom # Compare against vendor-provided firmware hash # Scan for known UEFI malware signatures yara -r uefi_malware_rules.yar firmware_dump.rom ``` ``` Known UEFI Malware Families: ━━━━━━━━━━━━━━━━━━━━━━━━━━ LoJax: First in-the-wild UEFI rootkit (APT28/Fancy Bear) Modifies SPI flash to drop persistence agent MosaicRegressor: Modular UEFI framework dropping multiple payloads CosmicStrand: UEFI firmware rootkit modifying kernel during boot BlackLotus: UEFI bootkit bypassing Secure Boot on Windows 11 ESPecter: ESP (EFI System Partition) bootkit modifying boot manager MoonBounce: SPI flash implant modifying CORE_DXE module FinSpy UEFI: Surveillance software with UEFI persistence ``` ### Step 5: Emulate Firmware for Dynamic Analysis Run extracted firmware in an emulated environment: ```bash # Emulate ARM-based IoT firmware with QEMU # Mount the extracted filesystem sudo mount -o loop squashfs-root.img /mnt/firmware # Chroot into the firmware with QEMU user-mode emulation sudo cp /usr/bin/qemu-arm-static /mnt/firmware/usr/bin/ sudo chroot /mnt/firmware /bin/sh # Or use firmadyne for automated firmware emulation # https://github.com/firmadyne/firmadyne python3 fat.py firmware.bin # Network service analysis within emulated firmware # Scan for open ports and services nmap -sV localhost -p 1-65535 # Monitor network traffic from emulated firmware tcpdump -i tap0 -w firmware_traffic.pcap ``` ### Step 6: Document Firmware Analysis Compile comprehensive firmware analysis findings: ``` Analysis documentation should cover: - Firmware image metadata (vendor, model, version, build date) - Extraction results (filesystem type, kernel version, architecture) - Modified files compared to known-good baseline - Backdoor binaries discovered with reverse engineering findings - Hardcoded credentials and unauthorized access mechanisms - Network services and their security posture - UEFI/BIOS integrity verification results - Extracted IOCs (IPs, domains, file hashes, SSH keys) - Remediation recommendations (reflash, replace, update) ``` ## Key Concepts | Term | Definition | |------|------------| | **Firmware** | Software permanently stored in device hardware (flash memory, EEPROM) controlling low-level device operations and boot process | | **UEFI (Unified Extensible Firmware Interface)** | Modern system firmware replacing legacy BIOS; provides boot services, runtime services, and a modular driver architecture | | **SPI Flash** | Serial Peripheral Interface flash memory chip storing UEFI/BIOS firmware; can be read and modified for persistence | | **Secure Boot** | UEFI feature verifying digital signatures of boot components to prevent unauthorized code execution during startup | | **SquashFS** | Read-only compressed filesystem commonly used in embedded Linux firmware for space-efficient storage | | **Bootkit** | Malware infecting the boot process (MBR, VBR, UEFI) to load before the operating system and evade OS-level security | | **Firmware Emulation** | Running extracted firmware in a virtual environment (QEMU, firmadyne) to analyze behavior without physical hardware | ## Tools & Systems - **binwalk**: Firmware analysis tool for scanning, extracting, and analyzing embedded file systems and compressed data in firmware images - **UEFITool**: Open-source UEFI firmware image parser and extractor for analyzing UEFI volumes, modules, and drivers - **chipsec**: Intel's open-source framework for platform security assessment including SPI flash, Secure Boot, and UEFI analysis - **firmadyne**: Automated firmware analysis and emulation platform for Linux-based embedded devices - **Ghidra**: NSA's reverse engineering tool with ARM, MIPS, and other embedded architecture support for firmware binary analysis ## Common Scenarios ### Scenario: Investigating a Compromised Router with Persistent Backdoor **Context**: A network router continues to exhibit suspicious behavior (unexpected DNS resolutions, traffic to unknown IPs) even after factory resets. Firmware-level compromise is suspected. **Approach**: 1. Dump the firmware from the router using JTAG/UART debug interface or vendor management tools 2. Extract the filesystem with binwalk and identify the Linux distribution and kernel version 3. Compare file hashes against known-good firmware image from the vendor 4. Search startup scripts (rcS, inittab, crontab) for backdoor entries 5. Analyze any modified or new binaries with Ghidra (ARM/MIPS architecture) 6. Check for hardcoded credentials, unauthorized SSH keys, and reverse shell scripts 7. Emulate the firmware to observe network behavior and identify C2 communication **Pitfalls**: - Not dumping firmware from the actual device (downloading from vendor site gives clean version, not the compromised one) - Ignoring modified shared libraries (.so files) that may hook system functions - Missing firmware modifications stored outside the main filesystem (bootloader, configuration partitions) - Not checking both the primary and backup firmware partitions (some devices have dual-bank flash) ## Output Format ``` FIRMWARE MALWARE ANALYSIS REPORT =================================== Device: NetGear R7000 Router Firmware Version: V1.0.11.116 (modified) Architecture: ARM (Little Endian) Filesystem: SquashFS (Linux 3.4.103) Dump Method: UART debug console INTEGRITY CHECK Vendor Firmware Hash: aaa111bbb222... (clean V1.0.11.116) Analyzed Firmware Hash: ccc333ddd444... (MISMATCH) Modified Files: 14 files differ from vendor baseline BACKDOOR FINDINGS [!] /usr/bin/httpd_backdoor (new binary, not in vendor firmware) Architecture: ARM 32-bit Function: Reverse shell to 185.220.101[.]42:4444 Persistence: Added to /etc/init.d/rcS [!] /etc/shadow modified Root password changed to known hash New user 'admin2' added with UID 0 [!] /etc/crontab modified Added: */5 * * * * /usr/bin/httpd_backdoor [!] /root/.ssh/authorized_keys (new file) Contains attacker's SSH public key EXTRACTED IOCs C2 IP: 185.220.101[.]42 C2 Port: 4444 SSH Key: ssh-rsa AAAA... attacker@control Backdoor Hash: eee555fff666... REMEDIATION 1. Flash clean vendor firmware via TFTP recovery mode 2. Change all device credentials 3. Update to latest firmware version 4. Enable firmware integrity checking if available 5. Monitor for re-compromise indicators ``` --- Source attribution: costrict-plugins-repo Original project: https://github.com/costrict-plugins-repo/mukul975-anthropic-cybersecurity-skills-cybersecurity-skills/blob/1b344d155f00bae5cf27d8eba9508e8f5050d904/skills/performing-firmware-malware-analysis/SKILL.md License: Apache-2.0 License information: https://www.apache.org/licenses/LICENSE-2.0 Original upstream instructions; downloaded from Mega AI Hub. ## Upstream license notice Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. Definitions. "License" shall mean the terms and conditions for use, reproduction, and distribution as defined by Sections 1 through 9 of this document. "Licensor" shall mean the copyright owner or entity authorized by the copyright owner that is granting the License. "Legal Entity" shall mean the union of the acting entity and all other entities that control, are controlled by, or are under common control with that entity. For the purposes of this definition, "control" means (i) the power, direct or indirect, to cause the direction or management of such entity, whether by contract or otherwise, or (ii) ownership of fifty percent (50%) or more of the outstanding shares, or (iii) beneficial ownership of such entity. "You" (or "Your") shall mean an individual or Legal Entity exercising permissions granted by this License. "Source" form shall mean the preferred form for making modifications, including but not limited to software source code, documentation source, and configuration files. "Object" form shall mean any form resulting from mechanical transformation or translation of a Source form, including but not limited to compiled object code, generated documentation, and conversions to other media types. "Work" shall mean the work of authorship, whether in Source or Object form, made available under the License, as indicated by a copyright notice that is included in or attached to the work (an example is provided in the Appendix below). "Derivative Works" shall mean any work, whether in Source or Object form, that is based on (or derived from) the Work and for which the editorial revisions, annotations, elaborations, or other modifications represent, as a whole, an original work of authorship. For the purposes of this License, Derivative Works shall not include works that remain separable from, or merely link (or bind by name) to the interfaces of, the Work and Derivative Works thereof. "Contribution" shall mean any work of authorship, including the original version of the Work and any modifications or additions to that Work or Derivative Works thereof, that is intentionally submitted to the Licensor for inclusion in the Work by the copyright owner or by an individual or Legal Entity authorized to submit on behalf of the copyright owner. For the purposes of this definition, "submitted" means any form of electronic, verbal, or written communication sent to the Licensor or its representatives, including but not limited to communication on electronic mailing lists, source code control systems, and issue tracking systems that are managed by, or on behalf of, the Licensor for the purpose of discussing and improving the Work, but excluding communication that is conspicuously marked or otherwise designated in writing by the copyright owner as "Not a Contribution." "Contributor" shall mean Licensor and any individual or Legal Entity on behalf of whom a Contribution has been received by the Licensor and subsequently incorporated within the Work. 2. Grant of Copyright License. Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare Derivative Works of, publicly display, publicly perform, sublicense, and distribute the Work and such Derivative Works in Source or Object form. 3. Grant of Patent License. Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section) patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer the Work, where such license applies only to those patent claims licensable by such Contributor that are necessarily infringed by their Contribution(s) alone or by combination of their Contribution(s) with the Work to which such Contribution(s) was submitted. If You institute patent litigation against any entity (including a cross-claim or counterclaim in a lawsuit) alleging that the Work or a Contribution incorporated within the Work constitutes direct or contributory patent infringement, then any patent licenses granted to You under this License for that Work shall terminate as of the date such litigation is filed. 4. Redistribution. You may reproduce and distribute copies of the Work or Derivative Works thereof in any medium, with or without modifications, and in Source or Object form, provided that You meet the following conditions: (a) You must give any other recipients of the Work or Derivative Works a copy of this License; and (b) You must cause any modified files to carry prominent notices stating that You changed the files; and (c) You must retain, in the Source form of any Derivative Works that You distribute, all copyright, patent, trademark, and attribution notices from the Source form of the Work, excluding those notices that do not pertain to any part of the Derivative Works; and (d) If the Work includes a "NOTICE" text file as part of its distribution, then any Derivative Works that You distribute must include a readable copy of the attribution notices contained within such NOTICE file, excluding any notices that do not pertain to any part of the Derivative Works, in at least one of the following places: within a NOTICE text file distributed as part of the Derivative Works; within the Source form or documentation, if provided along with the Derivative Works; or, within a display generated by the Derivative Works, if and wherever such third-party notices normally appear. The contents of the NOTICE file are for informational purposes only and do not modify the License. You may add Your own attribution notices within Derivative Works that You distribute, alongside or as an addendum to the NOTICE text from the Work, provided that such additional attribution notices cannot be construed as modifying the License. You may add Your own copyright statement to Your modifications and may provide additional or different license terms and conditions for use, reproduction, or distribution of Your modifications, or for any such Derivative Works as a whole, provided Your use, reproduction, and distribution of the Work otherwise complies with the conditions stated in this License. 5. Submission of Contributions. Unless You explicitly state otherwise, any Contribution intentionally submitted for inclusion in the Work by You to the Licensor shall be under the terms and conditions of this License, without any additional terms or conditions. Notwithstanding the above, nothing herein shall supersede or modify the terms of any separate license agreement you may have executed with Licensor regarding such Contributions. 6. Trademarks. This License does not grant permission to use the trade names, trademarks, service marks, or product names of the Licensor, except as required for reasonable and customary use in describing the origin of the Work and reproducing the content of the NOTICE file. 7. Disclaimer of Warranty. Unless required by applicable law or agreed to in writing, Licensor provides the Work (and each Contributor provides its Contributions) on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. You are solely responsible for determining the appropriateness of using or redistributing the Work and assume any risks associated with Your exercise of permissions under this License. 8. Limitation of Liability. In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall any Contributor be liable to You for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising as a result of this License or out of the use or inability to use the Work (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if such Contributor has been advised of the possibility of such damages. 9. Accepting Warranty or Additional Liability. While redistributing the Work or Derivative Works thereof, You may choose to offer, and charge a fee for, acceptance of support, warranty, indemnity, or other liability obligations and/or rights consistent with this License. However, in accepting such obligations, You may act only on Your own behalf and on Your sole responsibility, not on behalf of any other Contributor, and only if You agree to indemnify, defend, and hold each Contributor harmless for any liability incurred by, or claims asserted against, such Contributor by reason of your accepting any such warranty or additional liability. END OF TERMS AND CONDITIONS APPENDIX: How to apply the Apache License to your work. To apply the Apache License to your work, attach the following boilerplate notice, with the fields enclosed by brackets "[]" replaced with your own identifying information. (Don't include the brackets!) The text should be enclosed in the appropriate comment syntax for the file format. Please do not remove or change the license header comment from a contributed file except when necessary. Copyright 2026 mukul975 Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. # Mega AI Hub resource metadata Creator / publisher: costrict-plugins-repo Original project: https://github.com/costrict-plugins-repo/mukul975-anthropic-cybersecurity-skills-cybersecurity-skills/blob/1b344d155f00bae5cf27d8eba9508e8f5050d904/skills/performing-firmware-malware-analysis/SKILL.md Attribution basis: Source repository record Fields of work: Data & Analytics, Development & Engineering Roles: Data Scientist, ML / AI Engineer, Security Engineer Specialties: Specialty not specified Tools: Binwalk, Firmware Analysis Toolkit, Ghidra, Qemu, Uefitool Country applicability: Country not specified Classification basis: Source catalog labels Instruction SHA-256: d880494ef24812c6e1bf5d1a9b1b616b26373c8af0911496a3217e22d6503434