Christmas Tree (also known as CHRISTMA EXEC) was an early example of an email-related malware. The worm was blamed on a German student who claimed he just wanted to send greetings to his friends. In 1990, the Christmas Tree worm resurfaced, forcing IBM to shut down its 350,000 network of terminals. In 1999, the worm was used to send Christmas messages to other users in the U.S. The worm has since resurfaced.”]
Source: https://grahamcluley.com/christmas-malware-short-history/