Methods to protect flash memory parts against certain types of virus attacks.
Original Publication Date: 2002-Jun-11
Included in the Prior Art Database: 2003-Jun-21
A method is disclosed to prevent a certain class of virus attack. Today's personal computers incorporate a nonvolatile memory module that is typically used to store the systems BIOS code. The common technology for this module is referred to in the industry as "Flash" technology. This technology allows the module to be erased and reprogrammed in the event of a BIOS upgrade. When this technology was introduced in the 1980's, the number of erase rewrite cycles was limited (in the 100's on very early parts). If you exceeded this number of erase write cycles, the part would start to show failures during the rewrite. As the technology has matured, this limitation on erase write cycles has gone up by orders of magnitude (tens of thousands of cycles are typical in todays parts). The early flash update programs were all DOS based, requiring the user to boot a DOS diskette and provide several manual inputs. With this type of update scheme, it would be virtually impossible to exceed the erase rewrite limit of todays flash parts. However, recently there has been a push to make flash update a process that can be run under the operating system. While this adds convenience and flexibility to the process, it opens the door to a potential virus attack that could render the system unusable by merely invoking the flash update routine over and over. (Various ways can be envisioned to hide this activity from the end user such as only running the updates when the system was in a standby power state or only running the program when the screen saver was active). This sort of attack could, over a period of weeks or months, effectively "wear out" the flash part and leave the system with a nonfunctional BIOS.