It was also quite common in the 1980s to use physical floppy disks and the postal service for spreading software, in an activity known as "mail trading". Prior to the sale of software that came on CD-ROM discs and after hard drives had become available, the software did not require the floppy disc to be in the drive when starting and using the program. So, a user could install it onto his/her computer and mail the disk to the next person, who could do the same. Particularly widespread in continental Europe, mail trading was even used by many of the leading cracker groups as their primary channel of interaction. Software copyright violation via mail trading was also the most common means for many computer hobbyists in the Eastern bloc countries to receive new Western software for their computers.