Punters looking for a big win on Saturday's Grand National may find themselves under attack from hackers looking to cash in on online betting.
Webroot's Threat Research team has reported an increase in the number of keyloggers being rapidly updated by the malware authors who created them.
Nick Banks, managing director EMEA of Webroot's Consumer Business Unit, said, "Since January 2008, 44% of the keyloggers identified by our automated threat research method have been updated, while 28% of new keyloggers identified so far this year have already been updated.
"Hackers churn out updates or new variants to get past detection at the desktop, so that they can continue to harvest personal information unchallenged."
Online betting is expected to boom with many bookmakers offering new customers free bets worth between £10 and £100 if they bet online.
Webroot has developed a free computer scan tool to check for spyware, viruses and other threatening forms of malware.