Internet spies have targeted the European aerospace industry, British web security experts warned.
Researchers at internet security firm Sophos warned that an aerospace supplier was "deliberately targeted" in what is known as a "zero-day" attack, which exploited a previously unknown vulnerability in Microsoft's Windows operating system.
Cyber spies infected the company's website with malware, which then infects the computers of people visiting it -- giving the spooks invisible and total control over the infected system.
The vulnerability was first noticed this week by Google, which warned some of its Gmail users that there had been attempts to break into their accounts, or hack their computers using the hole in the Windows system.
The targeted nature of the attack led Sophos to speculate that it was likely a state-sponsored espionage operation, a sentiment echoed by Google.
Sophos also warned that now that the vulnerability had been identified on the internet, it would soon be used by outright criminal elements.
Graham Cluley, a cyber security consultant at Sophos, said, "It's just a matter of time before the money-stealing elements who operate on the internet start using it to harvest the accounts of ordinary people."
He added, "Don't underestimate the seriousness of this vulnerability. It's being actively exploited in the wild, and there is currently no patch available for it."
Microsoft published a "workaround" to paper over the gap in their system, but researchers are anxious that the software giant should publish a "patch" as soon as possible.