The warning has been splashed across Facebook and Google, and the FBI has set up a special website to help internet users to stay safe, the Daily Mail reported. The virus "spoofs" popular websites in an attempt to steal personal information.

The software found its way into thousands of computers worldwide last year. It redirects users away from trusted websites towards spoof websites in a bid to steal financial and personal information. When the attack was noticed, the FBI routed infected machines through its server to stop the attacks.

But the servers will be taken down July 9. When this happens, computers still infected are likely to lose their internet connection without warning.

Warnings about the problem have been splashed across Facebook and Google, and the FBI has set up a special website.

The number of computers infected is more than 277,000 worldwide. The number was 360,000 in April. Of those still infected, the FBI believes that about 64,000 are in the US.

Users still infected will have to call their service providers for deleting the malware and reconnecting to the internet.

Last year, when international hackers ran an online advertising scam to take control of more than 570,000 infected computers around the world, the FBI agents realised that if they turned off the malicious servers being used to control the computers, all the victims would lose their internet service.

The FBI then installed two clean internet servers to take over instead of the malicious servers so that people would not suddenly lose internet. But that temporary system will be shut down July 9.