Growth in online gaming has caused crooks to move in.
Gamblers and fantasy football fans are likely to be targeted by hackers as the new NFL season begins in the US, according to online security expert Robert Siciliano.
Hackers will look to exploit enthusiasm for sport to spread malware and collect personal data through drive-by downloads and email attachments, with the popularity of the industries thought to be a draw for crooks.
Writing on the McAfee blog, Siciliano said: "Participating in a fantasy football leagues and cyber gambling are two of the biggest attractors of cybercrime.
"With fantasy footballers searching online looking for in-depth information on their players, you could be exposing yourself to risk."
Online gambling has been a contentious legal issue in the US, with New Jersey, Delaware and Nevada the only states to allow online gambling on their territories.
Revenue from the industry has grown quickly since states moved to legalise the practice, and was thought to be approaching $10m per month in March of this year, according to research firm yStats.
The Fantasy Sports Trade Association estimates that 33 million Americans play fantasy sports, spending $3.6bn per year in the process.
Players are advised to be cautious when opening attachments, update security regularly, and monitor app permissions.