WASHINGTON (AP) _ Security researchers have detected hackers distributing software to break into computers using flaws announced last week in some versions of Microsoft Corp.'s Windows operating system.
The threat from this new vulnerability _ which already has drawn stern warnings from the Homeland Security Department _ is remarkably similar to one that allowed the Blaster virus to infect hundreds of thousands of computers last month.
The discovery Tuesday gives fresh impetus for tens of millions of Windows users _ inside corporations and in their homes _ to immediately apply a free repairing patch from Microsoft. Homeland Security officials have warned that attacks could result in a ``significant impact'' on the operation of the Internet.
Researchers from iDefense Inc. of Reston, Va., who found the new attack software being distributed from a Chinese Web site, said it was already being used to break into vulnerable computers and implant eavesdropping programs. They said they expect widespread attacks similar to the Blaster infection within days.
``It's fairly likely,'' said Ken Dunham, a senior iDefense analyst. ``Certainly we'll see new variants in the next few hours or days.''
Microsoft confirmed it was studying the new attack tool.
Last month's Blaster infection spread just days after hackers began distributing tools for breaking into Windows computers using a related software flaw. That infection disrupted computers at the Federal Reserve in Atlanta, Maryland's motor vehicle agency and the Minnesota transportation department.
The latest Windows flaws, announced Sept. 10, were nearly identical to those exploited by the Blaster worm. Computer users who applied an earlier patch in July to protect themselves still must install the new patch from Microsoft, available from its Web site.
Amy Carroll, a director in Microsoft's security business unit, said 63 percent more people have already downloaded the latest patch than downloaded the patch for last month's similar vulnerability during the same five-day period.
``We've continued to beat the drum, to give people better awareness,'' Carroll said. ``We have seen some success.''
The latest hacker tool was relatively polished. It gives hackers access to victims' computers by creating a new account with the name ``e'' with a preset password. iDefense said the tool includes options to attack two Windows 2000 versions that are commonly used inside corporations.
The tool being distributed Tuesday did not include an option to break into computers running Microsoft's latest operating systems, such as Windows XP or Windows Server 2003, but iDefense said it expected such modifications to make it more dangerous.