the acceleration of viruses and malware 

From Countdown to Zero Day, by Kim Zetter, loc 1000-1018:

When Chien joined Symantec, antivirus researchers were like the Maytag repairman in those iconic ads— they had a lot of downtime. Viruses were still rare and tended to spread slowly via floppy disks and the “sneaker net”— carried from one computer to another by hand. Customers who thought they were infected with a virus would mail the suspicious file on a floppy disk to Symantec, where it might sit in a desk tray for a week or more before Chien or one of his colleagues wandered by and picked it up. Most of the time, the files turned out to be benign. But occasionally, they found a malicious specimen. When that occurred, they dashed off some signatures to detect it, then threw them onto another floppy disk and mailed it back to the customer along with instructions for updating their virus scanner. 

It wasn’t long, though, before malware evolved and the landscape changed. The introduction of Microsoft Windows 98 and Office, along with the expanding internet and proliferation of e- mail, spawned rapid- spreading viruses and network worms that propagated to millions of machines in a matter of minutes. The Melissa virus in 1999 was one of the most notorious. Launched by a thirty- one- year- old New Jersey programmer named David Smith, it came embedded in a Word document that Smith posted to the newsgroup. Smith knew his target audience well— he enticed them to open the file by claiming it contained usernames and passwords to access porn sites. Once opened, Melissa exploited a vulnerability in the macro function of Microsoft Word and e- mailed itself to the first fifty contacts in the victim’s Outlook address book. Within three days the world’s first mass- mailing virus had spread to more than 100,000 machines, a spectacular record at the time, but quaint by today’s standards. In addition to spreading via Outlook, it slipped a nerdy Scrabble reference into documents on infected machines: “twenty- two, plus triple- word- score, plus fifty points for using all my letters. Game’s over. I’m outta here.” 

Melissa was relatively benign, but it opened the way to other fast- moving viruses and worms that would dominate headlines for years. 3 As the threat landscape expanded, Symantec realized it needed to halt infections faster, before they began to spread. When the company first entered the antivirus business, it was considered a good response time to turn a threat around— from discovery to delivery of signatures— within a week. But Symantec aimed to reduce this to less than a day. To accomplish this, the company needed analysts in multiple time zones to spot viruses in the wild when they first appeared and get signatures out to US customers before they woke up and began clicking on malicious e- mail attachments.