A new threat dubbed "Nine-Ball" has compromised up to 40,000 legitimate websites, which are, in turn, infecting users with an information-stealing Trojan, according to security vendor Websense.

Attackers are actively exploiting a gaping zero-day hole in versions 9 and earlier of Adobe Acrobat and Reader, the company has warned.

Microsoft plans to release eight patches on Tuesday - six for "critical" vulnerabilities - as part of its monthly security update.