Federal authorities will remotely uninstall the Coreflood botnet Trojan from some infected Windows PCs over the next four weeks.
Coreflood will be removed from infected computers only when the owners have been identified by the Department of Justice (DOJ) and they have submitted an authorization form to the FBI.
The DOJ's plan to uninstall Coreflood is the latest step in a coordinated campaign to cripple the botnet, which controls more than 2 million compromised computers.
Two weeks ago, the DOJ and the FBI obtained an unprecedented temporary restraining order that allowed them to seize five command-and-control (C&C) servers that managed Coreflood. Since then, the U.S. Marshal's Service has operated substitute C&C servers that have disabled the bot on most infected PCs.
Those actions have reduced Coreflood by 90% in the U.S. and nearly 75% in other countries, but the government wanted to do more.
"Additional time is needed, however, both to allow more antivirus vendors to release virus signatures for Coreflood and to complete the process of notifying Coreflood victims," the DOJ said in a memorandum filed Saturday.
On Monday, U.S. District Court Judge Vanessa Bryant granted the DOJ's request for a preliminary injunction. It expires May 25.
The FBI has also identified infected computers, and in some cases has linked names to the static IP addresses. Those are the PCs targeted for remote Coreflood eradication.
"While the proposed preliminary injunction is in effect, the Government also expects to uninstall Coreflood from the computers of Identifiable Victims who provide written consent," said the DOJ in the memo.
In that same memo, the DOJ said it was not required to ask permission of Judge Bryant before making its move. "The Government is not requesting explicit authorization from the Court to do so, because the written consent form obviates the need for such authorization," DOJ lawyers said.
The consent form does come with warnings, however.
"While the 'uninstall' command has been tested by the FBI and appears to work, it is nevertheless possible that the execution of the 'uninstall' command may produce unanticipated consequences, including damage to the infected computers," the authorization form reads.
FBI Special Agent Briana Neumiller, who has been involved in the Coreflood investigation and takedown, echoed that in a declaration supporting the government's request for more time to strike Coreflood.
"Removing Coreflood in this manner could be used to delete Coreflood from infected computers and to 'undo' certain changes made by Coreflood to the Windows operating system when Coreflood was first installed," Neumiller said. "The process does not affect any user files on an infected computer, nor does it ... access any data on the infected computer."
The DOJ and FBI did not say how many machines it has identified as candidates for its uninstall strategy, but told the judge that FBI field offices would be notifying affected people, companies and organizations.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is firstname.lastname@example.org.