Though the spread of the virus has slowed, the worm is programmed on Friday to shut down the part of Microsoft’s website that offers users a cure, making it harder to repair and prevent damage.

Experts are also worried that the worm could carry with it a “Trojan Horse,” which would allow hackers to remotely control infected computers, the WSJ reported. 

Microsoft and other software makers are coming under increasing pressure to boost security and reliability of its product.

“End users of software, particularly big business, are just sick and tired of taking the fall when software doesn’t work,” Jeffrey Payne, chief executive of Cigital Inc. told the WSJ. “It’s starting to cost them so much money that they are beginning to push back on companies like Microsoft.”