Microsoft's assurances that Windows XP will not make it easier for hackers to launch damaging Denial of Service (DoS) attacks across the Internet have been dismissed by the security expert who first alerted the company to the issue. The US software giant released a statement last week in which it said Steve Gibson, president of Gibson Research Group, was incorrect to claim that the implementation of "raw sockets" in its Windows XP operating system was a serious mistake. According to Microsoft it will not be possible for a hacker to run malicious software such as Trojan horses on a machine running Windows XP, thanks to the company's "war on hostile code." This means, according to Microsoft, that an XP machine could not take part in a DoS attack. Microsoft also defended its implementation of raw sockets by denying that raw sockets are a critical factor in DoS attacks. Responding to Microsoft's denial, Gibson, who in thirty years of programming has written many security programs, has now accused Microsoft of lying when it claims that "previous versions of Windows" also supported raw sockets. According to Gibson, Windows 98 and 95 did not, which is why many Trojan horses will not run on Windows machines. Unlike Windows 2000, where Gibson claims raw sockets were first fully implemented, Windows XP--which ships on 25 October this year--will be run by home PC users who will be less inclined and/or able to maintain the security of their system and keep up with software patches.