Hackers take advantage of reduced IT security staff during public holidays to infect corporate IT systems, according to research from security company FireEye.

The company found that the volume of emails with malware-infected attachments spikes around the US public holidays of Labour Day and Thanksgiving. This trend became more pronounced in 2011 as hackers learned which dates were the most effective for the email attachment vector of malware infections in 2010, the co

FireEye gathered its data from its network of corporate clients, which, according to FireEye’s senior scientist Darien Kindlund, represent a large portion of Fortune 500 companies.“If we look to see when the attacks are occurring, it’s pretty compelling that the attacks are gearing up their operations and launching them on or around major national holidays,” says Kindlund.

But while malicious email detections spike on Labour Day and Thanksgiving, FireEye found no equivalent spike over the Christmas or New Year period. Kindlund suggests that the shorter public holidays provide the perfect opportunity to infect an organisation via email.

“Information security teams tend to be lighter staffed around those holidays, but the attack has this fine line," he says. "If everyone in an organisation were to go on holiday, then no one would be there to open up an attachment. They are picking holidays that are ones where a significant number of people will still be working, but the security people are not necessarily fully staffed. That might explain why Christmas and New Years are not a rich target.”

"Hackers tend to review when their attacks were successful, and base more attacks around those dates, so we think that malicous email volumes may grow even more around Labour Day and Thanksgiving in 2012," he says.