Firmware is stored innon-volatile memory – eitherread-only memory (ROM) or programmable memory such asEPROM,EEPROM, orflash. Changing a device's firmware stored in ROM requires physically replacing the memory chip – although some chips are not designed to be removed after manufacture. Programmable firmware memory can be reprogrammed via a procedure sometimes calledflashing.[2]
Ascher Opler used the termfirmware in a 1967Datamation article, as an intermediary term betweenhardware andsoftware. Opler projected that fourth-generation computer systems would have awritable control store (a small specialized high-speed memory) into whichmicrocode firmware would be loaded. Many software functions would be moved to microcode, andinstruction sets could be customized, with different firmware loaded for different instruction sets.[3]
As computers began to increase in complexity, it became clear that various programs needed to first be initiated and run to provide a consistent environment necessary for running more complex programs at the user's discretion. This required programming the computer to run those programs automatically. Furthermore, as companies, universities, and marketers wanted to sell computers to laypeople with little technical knowledge, greater automation became necessary to allow a lay-user to easily run programs for practical purposes. This gave rise to a kind of software that a user would not consciously run, and it led to software that a lay user wouldn't even know about.[4]
As originally used, firmware contrasted with hardware (the CPU itself) and software (normal instructions executing on a CPU). It was not composed of CPU machine instructions, but of lower-level microcode involved in the implementation of machine instructions. It existed on the boundary between hardware and software; thus the namefirmware. Over time, popular usage extended the wordfirmware to denote any computer program that is tightly linked to hardware, includingBIOS on PCs,boot firmware on smartphones,computer peripherals, or the control systems on simpleconsumer electronic devices such asmicrowave ovens andremote controls.
In some respects, the various firmware components are as important as theoperating system in a working computer. However, unlike most modern operating systems, firmware rarely has a well-evolved automatic mechanism of updating itself to fix any functionality issues detected after shipping the unit.
A computer's firmware may be manually updated by a user via a small utility program. In contrast, firmware in mass storage devices (hard-disk drives, optical disc drives, flash memory storage e.g. solid state drive) is less frequently updated, even when flash memory (rather than ROM, EEPROM) storage is used for the firmware.
Most computer peripherals are themselves special-purpose computers. Devices such as printers, scanners, webcams, andUSB flash drives have internally-stored firmware; some devices may also permit field upgrading of their firmware. For modern simpler devices, such asUSB keyboards,USB mouses andUSB sound cards, the trend is to store the firmware in on-chip memory in the device'smicrocontroller, as opposed to storing it in a separateEEPROM chip.
Consumer appliances likegaming consoles,digital cameras andportable music players support firmware upgrades. Some companies use firmware updates to add new playable file formats (codecs). Other features that may change with firmware updates include the GUI or even the battery life.Smartphones have afirmware over the air upgrade capability for adding new features and patching security issues.
Since 1996, mostautomobiles have employed an on-board computer and various sensors to detect mechanical problems. As of 2010[update], modern vehicles also employ computer-controlledanti-lock braking systems (ABS) and computer-operatedtransmission control units (TCUs). The driver can also get in-dash information while driving in this manner, such as real-time fuel economy and tire pressure readings. Local dealers can update most vehicle firmware.
Flashing[6] is a process that involves the overwriting of existing firmware or data, contained inEEPROM orflash memory module present in an electronic device, with new data.[6] This can be done to upgrade a device[7] or to change the provider of a service associated with the function of the device, such as changing from one mobile phone service provider to another or installing a new operating system. If firmware is upgradable, it is often done via a program from the provider, and will often allow the old firmware to be saved before upgrading so it can be reverted to if the process fails, or if the newer version performs worse. Free software replacements for vendor flashing tools have been developed, such asFlashrom.
Sometimes, third parties develop an unofficial new or modified ("aftermarket") version of firmware to provide new features or to unlock hidden functionality; this is referred to ascustom firmware. An example isRockbox as a firmware replacement forportable media players. There are manyhomebrew projects for various devices, which often unlock general-purpose computing functionality in previously limited devices (e.g., runningDoom oniPods).
Firmware hacks usually take advantage of the firmware update facility on many devices to install or run themselves. Some, however, must resort toexploits to run, because the manufacturer has attempted to lock the hardware to stop it from runningunlicensed code.
The Moscow-basedKaspersky Lab discovered that a group of developers it refers to as theEquation Group has developedhard disk drive firmware modifications for various drive models, containing atrojan horse that allows data to be stored on the drive in locations that will not be erased even if the drive is formatted or wiped.[8] Although the Kaspersky Lab report did not explicitly claim that this group is part of the United StatesNational Security Agency (NSA), evidence obtained from the code of various Equation Group software suggests that they are part of the NSA.[9][10]
Researchers from the Kaspersky Lab categorized the undertakings by Equation Group as the most advanced hacking operation ever uncovered, also documenting around 500 infections caused by the Equation Group in at least 42 countries.
Mark Shuttleworth, the founder of the companyCanonical, which created theUbuntu Linux distribution, has describedproprietary firmware as a security risk, saying that "firmware on your device is theNSA's best friend" and calling firmware "a trojan horse of monumental proportions". He has asserted that low-quality,closed source firmware is a major threat to system security:[11] "Your biggest mistake is to assume that the NSA is the only institution abusing this position of trust – in fact, it's reasonable to assume that all firmware is a cesspool of insecurity, courtesy of incompetence of the highest degree from manufacturers, and competence of the highest degree from a very wide range of such agencies". As a potential solution to this problem, he has called for declarative firmware, which would describe "hardware linkage and dependencies" and "should not includeexecutable code".[12] Firmware should beopen-source so that the code can be checked and verified.
Custom firmware hacks have also focused on injectingmalware into devices such as smartphones orUSB devices. One such smartphone injection was demonstrated on theSymbian OS atMalCon,[13][14] ahacker convention. A USB device firmware hack calledBadUSB was presented at theBlack Hat USA 2014 conference,[15] demonstrating how aUSB flash drive microcontroller can be reprogrammed to spoof various other device types to take control of a computer, exfiltrate data, or spy on the user.[16][17] Other security researchers have worked further on how to exploit the principles behind BadUSB,[18] releasing at the same time the source code of hacking tools that can be used to modify the behavior of different USB devices.[19]
