(firmware) virus's exist but are very rare
. Researchers have demonstrated in a test environment proof-of-concept viruses
modify the flash BIOS or install a rootkit on the BIOS of some systems so that it could survive a reformat and reinfected a clean disk. This type of malware exists primarily in-the-wild and is not generic...meaning it's vendor specific and cannot modify all types of BIOS. Although in February 2015, Kaspersky Labs reported "persistent, invisible espionage malware inside the firmware of hard drives compatible with nearly all major hard drive brands: Seagate, Western Digital, Samsung"
. This particular threat targeted government and military institutions, telecom and energy companies, nuclear research facilities, oil companies, encryption software developers, and media outlets.
This is a quote from my Security Colleague, Elise
who works with the Emsisoft Anti-Malware Research Team.
Firmware is typically a small piece of software coded directly into a device (for example a video card or DVD writer) necessary for the device to function correctly. This code is highly device-dependent, different manufacturers and different models all require specific firmware. For that reason a firmware infection is not only highly unlikely but also very impractical for a malware writer. Someone who wants to create a successful infection not only needs to make sure the malware stays on the system (by making it harder to detect and delete), but also that it is distributed on a large scale. Deploying a firmware rootkit on a large scale is close to impossible as you'd have to write a lot of different versions for different hardware models.
UEFI (Unified Extensible Firmware Interface) was introducted as a replacement for traditional BIOS in order to standardize computer firmware through a reference specification. However, there are several companies that develop UEFI firmware and there can be significant differences between the implementations used by computer manufactures. These articles explain the complexity of the UEFI, secure boot protocol and exploitation.
Fortunately, it's highly unlikely you will encounter a BIOS-level scenario as it is not practical for attackers to use such an exploit on a grand scale. Malware writers would much rather target a large audience through social engineering
where they can use sophisticated but less technical means than a BIOS virus.