INTERNET users have been drawn into a row between two online businesses that has slowed internet speeds around the world. The global web problems came after a Dutch web-hosting company took umbrage at being dubbed a source of spam email, and retaliated by launching what has been called the world's largest web attack.

Last night, internet users found web browsing was taking longer than usual. In many cases it was impossible to watch online movies. Users of intensive applications such Netflix are thought to have been particularly badly affected. The interruptions came after Spamhaus, a not-for-profit spam-fighting group based in Geneva, temporarily added the Dutch firm, CyberBunker, to a blacklist that is used by e-mail providers to weed out spam.

CyberBunker is housed in a five-storey former NATO bunker and famously offers its services to any website "except child porn and anything related to terrorism". It has often been linked to behaviour that anti-spam blacklist compilers have condemned. Its response was to mount a huge 'denial of service attack'. This works by trying to make a network unavailable to its intended users, overloading a server with co-ordinated requests to access it.

Internet speeds around the world can be impacted by such large-scale DNS amplified DDoS attacks because the Internet relies on DNS to work — major interference with DNS can have consequences for services not necessarily being directly targeted by such an attack. Internet Service Providers should implement technologies that prevent hackers from spoofing victims' IP addresses. Second, network administrators need to close any and all open DNS resolvers running on their network.

"Anyone that's running a network needs to go to openresolverproject.org, type in the IP addresses of their network and see if they're running an open resolver on their network," said Prince. "Because if they are, they're being used by criminals in order to launch attacks online. And it's incumbent on anyone running a network to make sure they are not wittingly aiding in the destruction of the Internet."