Fraudsters are believed to have targeted tens of millions of people just hours after the Duke and Duchess of Cambridge introduced their new son to the world.
Analysts said the group launched its "malicious email campaign" yesterday evening.
Their messages - which feigned to be legitimate updates from a ScribbleLive customer's site - contained a link entitled "Watch the Hospital Cam".
Viewers who followed this - in the hope of catching a glimpse of the future king outside the Lindo Wing of St Mary's Hospital - would instead have been infected by the Zeus trojan which is designed to steal bank details.
Troy Gill, senior security analyst at web security firm Appriver, said: "These cyber criminals piggy-backed on the news of the royal birth.
"I anticipate they would have been sending tens of millions of emails, if not more than that.
"If you are infected by the Zeus trojan, there is a strong possibility that your banking and any other personal information that you have entered online is going to be harvested. The ultimate goal is to steal your money."
"This was a phishing email sent by cyber attackers to an unknown list and taking advantage of people's excitement and anticipation around the Royal Baby's name announcement. It is very disappointing that people who are genuinely interested in this historic event have been targeted."