As always-on broadband connections became the norm, and more and more viruses were released, it became essential to update virus checkers more and more frequently. Even then, a new zero-day virus could become widespread before antivirus companies released an update to protect against it.
Before internet connectivity was widespread, viruses were typically spread by infected floppy disks. Antivirus software came into use, but was updated relatively infrequently. During this time, virus checkers essentially had to check executable files and the boot sectors of floppy disks and hard disks. However, as internet usage became common, viruses began to spread online.
Also in 1988 a mailing list named VIRUS-L was started on the BITNET/EARN network where new viruses and the possibilities of detecting and eliminating viruses were discussed. Some members of this mailing list like John McAfee or Eugene Kaspersky later founded software companies that developed and sold commercial antivirus software.