A significant chunk (12 per cent) of all scanning attacks found on a broadband service provider's network are launched from the machines of its own subscribers. That's according to a study by traffic management firm Sandvine which says its findings dispel the idea the broadband security involves only policing the borders between external and internal networks. Subscribers need to be protected from each other as well as external malicious hosts, it concludes.

Most of these "internal attackers" are likely unsuspecting victims themselves, unwitting hosts to malware infections that turn their Windows PCs into zombie drones under the control of hackers. An infected subscriber often reports performance degradations and other problems to the help desk, oblivious to the real reason why their computer seems sluggish or is behaving strangely. All the while his (it's nearly always blokes who get their machine infected by viruses) machine is searching for other vulnerable hosts.

Related stories

• NetEvents The real reason Skype isn't as good as it was (23 February 2006)
• The enemy within (15 December 2005)
• Hack attack linked to annular eclipse (4 October 2005)
• P-cube goes hunting for zombie PCs (22 September 2004)
• Zombie PCs spew out 80% of spam (4 June 2004)
• Windows worms tax ISPs (27 May 2004)
• P2P swamps broadband networks (12 September 2002)