Many still vulnerable to Conficker

Sophos has sent an alert saying many users still have yet to patch their PCs against the exploit that makes them vulnerable to the Conficker worm.

Sophos’ senior technology consultant Graham Cluley, said in a blog post Thursday, the antivirus company found 11 percent of users who had taken an endpoint assessment test at its Web site did not have the Microsoft OS08-067 patch installed.

The patch, available since October last year, fixes a vulnerability which allows the Conficker worm to infect PCs.

The Conficker saga has been broiling for the last month or so, where it received a swarm of media attention leading up to Apr. 1–when it was expected to detonate. Its real effects were seen about a week later, when it started dropping a mystery payload on infected computers.

Microsoft has also put up a US$250,000 reward for information leading to the arrest and conviction of the criminals behind the worm.

Cluley said in his blog post the 11 percent of infected PCs is “pretty depressing news”, given the press coverage the worm has received.

“It appears that the percentage of computers not patched against the exploit is holding steady,” he added.

The goal of Conficker’s creators remains unclear. While researchers have said the worm’s payload dumping activity indicates a profit motive, such as stealing passwords or spam-generation, Conficker has yet to fully reveal its intended function.

There are a number of tests and checks online, including an eye chart from the endpoint assessment test for the Microsoft patch.

Sophos is offering a tool to remove the Conficker worm from infected PCs, as well.

Conficker’s autorun and social engineering guide

We wrote several diaries about Conficker (or Downadup, depending on the AV tool you are using). F-Secure posted some interesting information about the number of infections which is almost certainly in millions (and who knows how many machines will stay infected as the owners will not even notice anything).

One of the reasons for infecting so many machines is that Conficker uses multiple infection vectors:

1. It exploits the MS08-067 vulnerability,
2. It brute forces Administrator passwords on local networks and spreads through ADMIN$ shares and finally
3. It infects removable devices and network shares by creating a special autorun.inf file and dropping its own DLL on the device.

F-Secure also blogged about the autorun.inf file where they noticed that it contained a lot of garbage (about 60 kb of random binary data). This fooled some AV programs so they didn’t scan the device properly (otherwise, they would have picked up the referenced DLL also stored on the device).

After removing garbage, one can see a nice autorun.inf file containing all important keywords. This grabbed my attention:

[Autorun]

Action=Open folder to view files
Icon=%systemroot%\system32\shell32.dll,4
Shellexecute=.\RECYCLER\S-5-3-42-2819952290-8240758988-879315005-3665\jwgkvsq.vmx,ahaezedrn

So, as you can see, the first part, “Install or run program” is there because Vista detected an autorun.inf file containing the shellexecute keyword. However, the text comes from the Action keyword and the icon is extracted from shell32.dll (the 4th icon in the file) – and it’s the standard folder icon! This can easily fool a user in clicking this one and thinking it will open the USB stick in Windows Explorer instead of the second (the real one). The first option will run Conficker, of course. Very smart. For administrators among you, I would suggest that you disable AutoPlay in your environments, unless it’s really necessary. Depending on the environment you might even completely disable USB, if you don’t need it. The following article explain nicely how the AutoPlay feature works and how to disable it (http://technet.microsoft.com/en-us/magazine/2008.01.securitywatch.aspx). Or check this article on the Autorun registry key (http://support.microsoft.com/kb/953252). UPDATE – fixed a typo in the vulnerability, it is MS08-067 (not MS08-068) – Nick Brown sent a URL to his blog where he described another method for disabling Autorun by modifying the IniFileMapping registry key, see more at http://nick.brown.free.fr/blog/2007/10/memory-stick-worms.html