The Code Red worm disturbs the Pentagon's computer networks as it finds more Web servers to infect.
"The worm is an ugly thing," US Army Major Barry Venable said in a telephone interview from Colorado Springs, where the US military monitors its networks.
"Here at (the Department of Defence), we've observed several disturbances to our networks as a result of this thing working on the Internet, but we've seen no significant degradation," Venable said.
Code Red surreptitiously infects computers running the Windows NT or 2000 operating systems and Microsoft IIS Web server software and then makes infected machines scan the Internet for more victims.
The Defence Department, which operates hundreds of Web sites, had to temporarily shut down public access to them during the July onslaught of Code Red.
Venable would not elaborate on whether the overnight "disturbances" included slow operation or whether any systems were shut down, but he said, "We will continue to evaluate the threat that it (Code Red) poses."
