Adversaries may modify system firmware to persist on systems.The BIOS (Basic Input/Output System) and The Unified Extensible Firmware Interface (UEFI) or Extensible Firmware Interface (EFI) are examples of system firmware that operate as the software interface between the operating system and hardware of a computer.[1][2][3]
System firmware like BIOS and (U)EFI underly the functionality of a computer and may be modified by an adversary to perform or assist in malicious activity. Capabilities exist to overwrite the system firmware, which may give sophisticated adversaries a means to install malicious firmware updates as a means of persistence on a system that may be difficult to detect.
| ID | Name | Description |
|---|---|---|
| S0047 | Hacking Team UEFI Rootkit |
Hacking Team UEFI Rootkit is a UEFI BIOS rootkit developed by the company Hacking Team to persist remote access software on some targeted systems.[4] |
| S0397 | LoJax |
LoJax is a UEFI BIOS rootkit deployed to persist remote access software on some targeted systems.[5] |
| S0001 | Trojan.Mebromi |
Trojan.Mebromi performs BIOS modification and can download and execute a file as well as protect itself from removal.[6] |
| ID | Mitigation | Description |
|---|---|---|
| M1046 | Boot Integrity |
Check the integrity of the existing BIOS or EFI to determine if it is vulnerable to modification. Use Trusted Platform Module technology. [7] Move system's root of trust to hardware to prevent tampering with the SPI flash memory.[5] Technologies such as Intel Boot Guard can assist with this. [8] |
| M1026 | Privileged Account Management |
Prevent adversary access to privileged accounts or access necessary to perform this technique. |
| M1051 | Update Software |
Patch the BIOS and EFI as necessary. |
| ID | Name | Analytic ID | Analytic Description |
|---|---|---|---|
| DET0099 | Detection Strategy for T1542.001 Pre-OS Boot: System Firmware | AN0275 |
Unexpected write operations to BIOS/UEFI firmware regions or EFI boot partitions that do not correlate with legitimate vendor firmware updates. API calls or utilities such as fwupdate.exe or vendor flash tools executed from non-administrative or non-IT management accounts. Suspicious raw disk writes targeting System Firmware GUID partitions followed by abnormal reboot sequences. |
| AN0276 |
Unauthorized firmware uploads to routers, switches, or firewalls via TFTP/FTP/SCP. Logs showing boot variable or startup image path changes redirecting to non-standard firmware images. Abnormal reboots or firmware rollback attempts following configuration modification events. |