Updating anti virus software
There’s no mass-mailing, there’s no requirement for a user to run an infected program.
On infected machines, the virus also converted the local drive(s) to open shares, providing remote access to anyone with malicious intent.
And updating antivirus solutions became critical once worms came to stay.
Melissa, which appeared in March 1999, marked a quantum leap forward in terms of speed of infection.
Boot sector viruses relied on the exchange of floppy disks in order to spread.
Things changed significantly when macro viruses appeared in 1995, since they were able to piggyback all emails sent by the infected user.