A computer worm that exploits a months-old Windows bug has infected more than a million PCs in the past 24 hours, a security company said Wednesday.
Early last Wednesday, Finnish security firm F-Secure Corp. estimated that 3.5 million PCs have been compromised by the “Downadup” worm, an increase of more than 1.1 million since the day before.
“[And] we still consider this to be a conservative estimate,” said Sean Sullivan, a researcher at F-Secure, in an entry to the company’s Security Lab blog.
On Tuesday F-Secure said the worm had infected an estimated 2.4 million machines.
The worm, which several security companies have reported surging dramatically during the last few days, exploits a bug in the Windows Server service used by all supported versions of Microsoft Corp. ‘s operating system, including Windows 2000, XP, Vista, Server 2003 and Server 2008.
Microsoft issued an emergency patch in late October, fixing the flaw with one of its rare “out of cycle” updates.
The soaring number of infections by Downadup-also called “Conficker” by some security companies-prompted Microsoft to add detection for the worm to its Malicious Software Removal Tool (MSRT), the anti-malware utility that the company updates and redistributes each month to Windows machines on Patch Tuesday.
The MSRT scans for known malware, then scrubs the system of any it finds.
Like researchers at firms such as Symantec Corp. and Panda Security, Microsoft blamed lackadaisical patching for the infections.
“A number of our customers have contacted our support team for assistance with containment in environments that were, largely, not patched when the worm was released,” said Cristian Craioveanu and Ziv Mador, two researchers at Microsoft’s Malware Protection Center, in a Tuesday blog entry.
“Either security update MS08-067 was not installed at all or was not installed on all the computers.”
Craioveanu and Mador said that the highest number of infection reports had come from the U.S., Canada, Mexico, Korea and several European countries, including the U.K., France and Germany.
Yesterday, F-Secure also reported that it was spying on Downadup’s command and control process by registering domains it thought the worm would try to use to download additional malware to infected PCs.
The worm, said Mikko Hypponen, F-Secure’s chief research officer, generates hundreds of possible domain names daily using a complex algorithm.
“This makes it impossible and/or impractical for us good guys to shut them all down,” acknowledged Hypponen in a blog entry.
“The bad guys only need to predetermine one possible domain for tomorrow, register it, and set up a website, and they then gain access to all of the infected machines. Pretty clever.”
Even so, F-Secure has registered some of the possible hosting domains so that it can eavesdrop on the attackers and get an idea of the number of infected PCs.
Other security firms have tried to pre-empt hackers by registering domains that they may use, but with mixed results.
Last November, FireEye Inc. tried to stay ahead of criminals operating the “Srizbi” botnet by registering several hundred domains being used to resurrect the infected PC army, but had to give up the game when it got too costly.
“We have registered a couple hundred domains,” said Fengmin Gong, chief security content officer at FireEye, at the time. “But we made the decision that we cannot afford to spend so much money to keep registering so many [domain] names.”
As soon as FireEye conceded, the hackers were able to reestablish communication with their bots.
Microsoft recommended that Windows users install the October update, then run the January edition of the MSRT to clean up compromised computers.
It’s not clear whether the hackers behind Downadup are building a botnet of their own, said Joe Stewart, a senior security researcher at SecureWorks Inc., in an interview today.
For the moment, they seem satisfied feeding victims fake security software, which pesters users with pop-ups until they pay for the worthless program.
F-Secure’s Hypponen, however, sounded worried about the possibility that machines infected with Downadup would be converted into bots. “It would make for one big badass botnet,” he said.
SQL injections
SQL injection is one technique that hackers often use to recruit more computers on to a botnet. This is a code injection technique that exploits a security vulnerability in the database layer of an application.
The most common variety of the hack is a direct insertion of code into a place where a user inputs information. That gives hackers an opportunity to inject SQL commands that are executed blindly by the server.
A high-profile instance of SQL injection was witnessed last year when video game fans surfing on the Sony Playstation Web site were subjected to a pop-up window that displayed a fake virus scan running, followed by a message their computer was ridden with viruses and Trojans.
Then the surfer was offered a fake anti-virus software package for a fee.
SQL injection is an “extremely effective” method of attack that can be easily hidden in the nooks and crannies of Web code, says Graham Cluley, senior technology consultant with Sophos plc headquartered in Abingdon, U.K.
The problem lies with a lack of rigorous checking of code by the administrators affected.
“If they’re not doing proper checking, hackers can start to embed and inject code into their database,” the consultant explains. “[The database] ends up peppered with small pieces of code calling up third-party Web sites.”
Last July Microsoft responded to the SQL Server user community last week with two free tools and a security advisory to help Web admins safeguard against SQL injection.
Here are the tools and tips passed on by Microsoft and Bourne:
Detect: Hewlett Packard has developed a free scan that can identify whether a Web site is susceptible to SQL injection attacks. HP Scrawlr can be downloaded at the HP Security Center.
Test: Toronto-based company Security Compass has a suite of plug-in tools that can be used with the Firefox browser. Web developers have the convenience of looking for SQL injection vulnerabilities with the click of a button. Download SQL Inject-Me.
Defend: Scrutinize more carefully the HTTP requests being made by SQL commands on a Web site.
A Microsoft security tool will allow you to put restrictions on what the Internet Information Services will process from the server. It could block harmful requests from ever getting to the Web application. Download URLScan Tool 3.0 Beta.
Identify: For those using ASP code on their Web sites, another Microsoft tool can analyze the code and then output a display of the areas that are vulnerable to SQL injection.
The tool also comes with documentation that actually tells users how to fix the different problems that could be found in the code analyzed. Download the Microsoft Source Code Analyzer for SQL Injection at Microsoft Knowledge Base Article 954476.
Fixing the actual root of the problem is important, Cluley says. A Web site that simply removes the injected code but doesn’t patch up the exploit will find the code is re-inserted in short order by automated botnets.
Source: ComputerWorld. With files from Brian Jackson
