A distributed denial-of-service (DDoS) attack severely disrupted Sweden's police administration web site earlier this week.

The attacks flooded the site with information requests, causing the servers to crash and take the site offline. At its peak the attack caused traffic to spike from 800 requests a second to more than 400,000, according to Swedish news site The Local.

The attack also took down as many as 40 media sites also being hosted by service provider Basefarm. The Local reported that, as of Friday evening Swedish time, neither the hosting firm nor police investigators knew who was behind the attacks or their motive for taking the sites down.

DDoS attacks have grown increasingly popular as a form of protest and cyber warfare. Multiple computers and botnets are used to flood sites with traffic, causing servers to crash and taking sites offline for extended periods of time.

The tactic has been employed as a cyber warfare tool in particular by groups in Eastern Europe. Russian groups were believed to be behind DDoS attacks on government sites in Georgia, and to have rented botnets to attack Estonia.

Earlier this year, attackers also took at aim government sites in South Korea, using machines infected with the MyDoom botnet worm to take sites offline.