The CRTC has issued its first warrant under the federal government's anti-spam legislation to take down a Toronto-based malware server in an attempt to disrupt an international network of infected computers.

The move was part of a co-ordinated effort between Canadian authorities, overseas law enforcement including Interpol and the U.S. Federal Bureau of Investigation, and Microsoft Corp.

The CRTC said the Toronto server acted as a command-and-control point for the Win32/Dorkbot malware, a family of related computer worms that spread through USB keys and instant messenging services and can steal usernames and passwords by watching your online activity.

A computer infected with Dorkbot can also download other malware and compromise a system further, as well as join other computers as part of a network called a "botnet" to attack a targeted server using a technique called a distributed denial of service attack. That involves sending multiple requests that overwhelm the server's capacity to respond, disabling it.

Canada's telecoms regulator gained new powers over the internet when Ottawa's anti-spam legislation came into effect in July 2014.

This is the first time the CRTC has used those powers to take down a server distributing malware on the Internet.