August 30, 2002

Microsoft issued a high-level security alert Thursday, saying all versions of its Windows operating system released since 1998 contain a critical flaw that could block a user from accessing e-mail and other data. The flaw could allow a hacker to delete so-called ``digital certificates'' that are used to encode and decode sensitive information. If such certificates were removed from a person's computer, the user would not be able to decode encrypted e-mail or other files, said Scott Culp, manager of Microsoft's security response center. When visiting certain Web sites, a warning box would pop up saying the site's identity could not be verified. But the flaw would not allow a hacker to access the user's e-mail, files or data, he said. 7:18:23 AM