The popularity of Facebook and other popular social networking sites has given hackers new ways to steal both money and information, the security company Sophos said in a report released on Wednesday, Reuters reports. About half of all companies block some or all access to social networks because of concerns about cyber incursions via the sites, according to the study. "Research findings also revealed that 63 percent of system administrators worry that employees share too much personal information via their social networking sites, putting their corporate infrastructure — and the sensitive data stored on it — at risk," the Sophos report said. This is despite years of exhortations to computer users that they should keep personal information private and refrain from opening attachments to emails from unfamiliar sources. One result is that a quarter of businesses have been hit by spam, phishing or malware attacks via Twitter or social networking sites, Sophos said.