4k is a computer virus which infects COM files and EXE files. The virus was one of the first to employ Stealth tactics, infected systems will hang, displaying the message Frodo Lives, on the 22 September, which is also the date of birth Bilbo Baggins, a character from the The Lord of the Rings.
This virus was spread without the aid of the Internet. It was ported between systems by floppy disks.
Raymond Glath of Phoenix, AZ, was the developer and owner of the Vi-Spy product which continued production until mid-release of Windows 95. Reports to McAfee antivirus and Vi-Spy antivirus firms resulted in only one product properly detecting the virus, Vi-Spy.
The virus added itself to the system in a way which defied normal infection processes. Because of this, it was able to infect a system without using system subroutines, which is what most antivirus products were watching. This is why the virus received the additional name 'stealth'. The infection process used a mathematical algorithm to determine the letters E-X-E & C-O-M. When a file was opened by the OS, the virus checked the extension of the file, and sometimes, other extension letters would be identified as a program file causing the virus to infect a data file and obviously corrupting its contents
Because the virus appended itself to a file, without updating the disk FAT (File Allocation Table) as to the new file length, the system would cross-link files and fill up disks with allocation errors. This would damage programs and data alike. The description of the problems found while trying correct the 'stupid-looking errors' would cause most computer professionals to erase the system and start over. A few days later the problems would arise again. Diagnostic disks and installation disks used to fix the computer would commonly be infected with the virus and this would aid in the spread.