Trackswap, also known as Xboot is a Bulgarian boot sector virus on MS-DOS that originated around 1989. It is a part of the "Plovdiv" group of viruses, named for the fact that they were created by a programmer from Plovdiv, Bulgaria.
A timeline on the history of computer viruses placed on the IBM incorrectly states that this virus contains the text string "(C) June, by the CIA.". This string is actually contained in a virus that was first discovered in Israel named "Swap". They are both boot sector viruses but do not seem to be related.
This is one of the first known boot sector viruses ever discovered.
When a floppy disk infected with the virus is booted, the virus becomes memory resident. It also infects the boot sectors of some floppy disks inserted into the system. It then infects the system's boot.
- F-Secure Antivirus, F-Secure Virus Descriptions : Xboot.