Nasty Nimda Nicks the Net

The latest worm to wreak havoc on the Net was still spreading across corporate networks at the end of last week, but rapid response was squishing many Nimda outbreaks.

The latest worm to wreak havoc on the Net was still spreading across corporate networks at the end of last week, but rapid response was squishing many Nimda outbreaks.

"This will definitely be the biggest malicious code event of the year," said Roger Thompson, security firm TruSecures technical director of malicious code research.

I-managers were trying to prevent infection and were mopping up if they were hit, while experts suggested how to avoid future damage.

"Things like PCs, I would suggest you just clean those," said Dan Ingevaldson, team leader of Internet Security Systems X-Force research team. This means downloading the latest software from antivirus vendors such as, Symantec or Trend Micro; performing system scans; and cleaning infected files.

Servers are more difficult to deal with once hit by Nimda. "In the case of a Web server or something that has regular backups, I would recommend you build from scratch," Ingevaldson said. This means formatting the machine and cleaning it completely, before reinstalling software and files from backup tapes.

New tools recently made available prevent such attacks from affecting companies. For instance, intrusion prevention systems - such as those available from Entercept Security Technologies, Okena and Ubizen - monitor applications to detect if their behavior deviates from the norm, such as Microsoft Outlook attempting to mail an attachment to every address in the address book. Before the command can be executed, these systems kick in and stop it. So, while a machine may still get infected with a virus, it wont behave as though it has.

"We were able stop Nimda from infecting any of the servers we were running on, without any updates or additions," said Chad Harrington, Entercepts product marketing manager.

Although the worm was discovered almost exactly a week after the Sept. 11 terrorist attacks, Attorney General John Ashcroft said authorities were not aware of any connection.

The numerous ways of contracting Nimda include: e-mail attachments, vulnerabilities in Microsoft Internet Information Server (IIS) and access through shared network drives. When using some versions of Microsoft Outlook, users dont even need to open the attachment - usually called README.EXE - to be infected; highlighting the e-mail message is enough.

"[Nimda] takes all the best things about Code Red I, Code Red II, Melissa and ILOVEYOU and rolls them into one," Ingevaldson said.

Despite the fact that the worm was striking Microsofts bug-plagued IIS as well as Outlook, the software giant was downplaying the danger. "Based on our understanding of this worm, if customers have taken the necessary precautions . . . they should be protected," a Microsoft statement said. The company added that it is working with the antivirus community, security experts, and appropriate government and industry organizations to thoroughly investigate the worm.

Experts from Exodus Communications discovered Nimda wasnt just designed to compromise computer systems, but to take over and manipulate them as well. Exodus expects hundreds of thousands of machines to be infected by Nimda, which would make recovery very costly.

While cleaning up PCs with antivirus software may be enough, servers should be treated more delicately, experts said. If administrator access has been provided to a hacker, its difficult to tell if anything on the server has been altered since the infection. Its better just to start from scratch and be safe.

Thats not a cheap proposition, said Alan King, president of King Consulting, a small IT consulting firm. King said that rebuilds typically take approximately two hours per server. At $100 per hour for the technicians time, large organizations are looking at spending hundreds of thousands of dollars before they even figure in the cost of any data loss.

King said he used to advise clients to update their antivirus software once or twice per month. "With the virus activity nowadays, I changed it to every single day. And as you can see, even that isnt enough," he said.