What is the most costly trojan horse in history?

The most pricey bug in history is the Love Bug virus, which was launched in 2000.  https://zerogov.net/?p=862 This infection caused an approximated $5.5 billion in damage worldwide, making it the most costly infection ever. The Love Bug virus was a mass-mailing worm that infected over 45 million computer systems in simply a couple of days. The virus spread rapidly by emailing itself to everybody in the victim's address book. Once a computer system was infected, the infection would delete essential files and spread itself to other computer systems. The Love Bug virus was ultimately stopped by a team of anti-virus scientists who created a vaccine that might protect computer systems from the virus.