The malicious software takes control of devices and forms them into a collection of attacking machines

Internet companies are bracing for more trouble after hackers released the code behind one of the most powerful online attacks ever, which harnessed as many as one million internet-connected devices to knock a blogger offline.

The malicious software takes advantage of weak security on video recorders, routers and other internet-connected devices, taking control of the systems and forming them into a collection of attacking machines, called a “botnet.” It can then disable a victim’s internet servers by flooding them with an overwhelming amount of internet traffic.

The botnet code was released Friday - apparently after a dispute between developers - and is now available for anyone to download, meaning more attacks are likely. By Tuesday, it had infected an estimated 300,000 devices, along with nearly one million infected using an earlier version of the software, according to Level 3 Communications. Some machines were hijacked by both strains.