You must have heard that there are a number of new variants of the long lived WORM_BAGLE. Well, that’s because of UPolyX.

UPolyX is not new, in fact its first version UPolyX v0.1 has been around since 2004. By searching through the net, it has four (4) versions in existence.

UPolyX is basically a scrambler. It specifically needs a UPX packed input file to produce an output file. Through its polymorphic decrypter engine, it can produce a number of different output files even on one input file. That’s why we are receiving a number of WORM_BAGLE variants from time to time.

The latest version of the scrambler which is, UPolyX v0.5, has added some permutation module to further improve its polymorphism.

The scrambler also implements an Executable Trash Generator or ETG that places trash (dummy instructions) in between the polymorphic decryptor and the code itself. ETG can be configured to control the number of bytes of trash to generate. ETG 1.00 is the only version known in the public and has been around since March 2000.

From the characteristics mentioned above, it seems like the authors primary purpose is to defeat the decryptor emulation techniques of various Anti-Virus engines.

Using this technology of the UPolyX, a detected malware can still be relived and get into the wild again.

So far as what I have noticed, the type of samples that we received are based on this principle:

Detected Malware + UPX + UPolyX (polymorphic decrypter + Executable Trash Generator) = New Undetected Malware


What if some worm authors decided to embed UPolyX’s technology? Hmm.. oh well, we might have a hard time to tell which variant of the worm is in the wild!
But, that’s just one of the possibilities, some may come along the way and that’s another story.:=)

From some time now, we have been checking the download site of the WORM_BAGLE.DA for changes in the uploaded file. When I checked the main site of the download url, which is http://{blocked}i.ru, I discovered that the site was a website for a LEGITIMATE Russian Company.

The author/s of the Bagle Malware just hacked the website and put the malware file on the http://{blocked}i.ru/img/ as 2.jpg, disguising itself as a jpg file of the legitimate website.

This may have been done by the malware author/s to avoid getting caught, since the site will not be traced to them.

Again we are experiencing a storm of TROJ_BAGLES coming in. The attachment of the TROJ_BAGLE being 19_09.exe.

As I said in my previous blog we were downloading the files from the urls used by bagle. To my surprise a new sample of the WORM_BAGLE was downloaded in this site http://{blocked}/img/2.jpg! Curiousity kicked in and im in hyper mode…

After some googling, I confirmed that the packer used in this WORM_BAGLE variant (UpolyX) is a polymorphic UPX scrambler. There you go Polymorphic!

After a while I downloaded again the file from the same url. Guess what I now have a new WORM_BAGLE variant.

So this may mean two things

• 1. From time to time a batch file maybe automatically replacing the uploaded file in http://{blocked}/img/2.jpg with a repacked version of the file. And since its packer is UpolyX, it has now changed appearance.
  
• 2. The malware writer may manually repack his WORM_BAGLE and manually change the file uploaded in the said site.

So after downloading the files, heres what I got…

• Four (4) variations of WORM_BAGLE.DA (Undetected)
  
• Four (4) variations of TROJ_BAGLE.DA (3 Detected and 1 Undetected)
  
• One (1) TROJ_DLOADER.ACT (Undetected)

Each TROJ_BAGLE.DA is already embedded in the WORM_BAGLE.DA 4 different worms also carries 4 different trojans.

MD5 Hash of files located below

• 2B855271E01342FD7ED6E0A2A6042947 2.jpg – WORM_BAGLE.DA
  
• 33E8E59AA5773978E4E9AA1B0DB28A4E 20_09.exe – DETECTED AS TROJ_BAGLE.DA
  
• 07BE19293429F833C284A1D96448E8DE 2.jpg – WORM_BAGLE.DA
  
• AAD4A3C6E090E2687320F19E4F3F8034 19_09.exe – TROJ_BAGLE.DA
  
• 8F2CF4AAE13C4F8588E92B97D522CD1C 2.jpg – WORM_BAGLE.DA
  
• 555573598640743DDE5C2DF992E5CBE3 02.exe – DETECTED AS TROJ_BAGLE.DA
  
• 9E6F3B0BA3D101CED7A3B0861B69865E 2.jpg – WORM_BAGLE.DA
  
• 2E5E131E4D5A6500B94F68D1C11FFCC5 09.exe – DETECTED AS TROJ_BAGLE.DA
  
• 609883018B90A6F4D36641F4D7F482F3 osa6.gif – TROJ_DLOADER.ACT

Note: By different, what I mean is the hex view(different because of the UpolyX packer). The behavior of the four files are the same.

A new batch of Mytob link emails is currently spreading. It uses the same technique as the one posted a while back.

The link which is found on the emails spread by Mytob downloads a file named Confirmation.pif.

This file is actually a Self Extracting Rar archive file containing a malware package.
Some files included are the WORM_MYTOB that spreads the email and a BOT malware.

According to a report made by Mark Toshack of MessageLabs, this new Mytob also installs an adware from http://{blocked}.matcash.com. It is said that the author gets $0.15 each each time the adware program is installed.

Just an additional info for WORM_BAGLE.DA.

After the bagle storm yesterday, we were still receiving reports that new bagle variants were being seen. So we decided to again download the links found on the WORM_BAGLE, TROJ_BAGLE and TROJ_DLOADER. I didnt find a new bagle variant, although i’m still downloading from the links, what I found out is a completely different thing.

On WORM_BAGLE.DA download links, there are 8 download links which connects to a web.php, 2 links were already down while the other 6 were downloaded successfully.

http://{blocked}/web.php

Inside the file web.php, are the email addresses used by WORM_BAGLE in its FROM FIELD. This may also be the reason why I couldnt simulate the E-Mail propagation of the worm since I tested it on an environment without internet connection. Each download link contains a different domain and name.

On one web.php

• tom@atomate.com
  
• tom@atomco.com
  
• tom@atomcreation.com
  
• tom@atomdigitaldesign.co.uk
  
• tom@atomic.com.au
  
• tom@atomic4.com
  
• tom@atomicamps.com
  
• tom@atomicblender.com
  
• tom@atomicdesign.tv
  
• tom@atomicdesigninc.com
  
• tom@atomicdog.com
  
• tom@atomicmarketing.com
  
• tom@atomicspatula.com
  
• …

and on another

• shkim301@korea.com
  
• shkim303@ktsolution.co.kr
  
• shkim303@ktsolutions.co.kr
  
• shkim304@hanmail.net
  
• shkim304@samsung.co.kr
  
• shkim3057@hanmail.net
  
• shkim30@daewoo.com
  
• shkim30@famecs.co.kr
  
• shkim30@hanmail.net
  
• …

yet on another

• kathleen@kent.net
  
• kathleen@kenwoodcc.net
  
• kathleen@keogh.net.au
  
• kathleen@kephart.net
  
• kathleen@keplers.com
  
• kathleen@keromail.com
  
• kathleen@kerraisle.com
  
• kathleen@kerstondesignteam.com
  
• kathleen@kertzmanweil.com
  
• …

Also WORM_BAGLE.DA downloads a file from this link http://{blocked}/sss.php and saves it as re_file.exe. However the link is still down as of the moment.

Berend-Jan Wever, aka “Skylined”, released an exploit code for the IDN host name heap buffer overrun vulnerability in Mozilla browsers. Mozilla browsers include (Firefox, Mozilla, and Netscape). You can find the source code of the exploit here.



These two lines are worth noticing in the exploit code.



If succesful, the exploit will set up a listening port at 28876. The exploit was tested to work in Firefox 1.0.6.

Skylined is previously known for his InternetExploiter series of exploits against MS IE and the Alpha 2 alphanumeric shellcode encoder, among others.

Firefox fix

Firefox 1.0.7 has been released to address this vulnerability, and is now available for download at the Mozilla Foundation homepage. MozillaZine also issued a security bulletin announcing the release of the Firefox fix. To quote the bulletin

The tandem of a Trojan and a worm is now becoming a favorite technique of malware authors for a more successful propagation or attack of their malicious programs. The combination of a Trojan and a worm started from the Troj_Bagle downloading the Worm_Bagle. However, another example of the trojan-worm tandem technique being noticed is in this new TROJ_DROPPER.LV and WORM_MYTOB.KM.

Instead of downloading the Mytob worm, TROJ_DROPPER.LV drops a copy of WORM_MYTOB.KM and a WORM_SDBOT.CHA in the affected system. Then, WORM_MYTOB.KM mass mails an email message containing a link which points to TROJ_DROPPER.LV. Thus, when a user clicks on the link found in the email, the Trojan dropper is downloaded.

This technique can bypass the filters used in email scanning applications that scans or blocks malicious attachments. A good social engineering would then complete the intention of the malware enticing a user to click on the malicious link found in the mail.

The URL link was submitted to the web-blocking query so we have no problem when a user clicks on the malicious link of this malware since it is already blocked in the server.

At the end of my boring shift, e mails started arriving and soon I was wide awake.
The emails contained in it a copy of a WORM_MYTOB, this is easily distinguished because of the hellmsn.exe drop file and other common WORM_MYTOB traits…or so I thought. :)
After I few minutes of looking at the malware body, I realized that it is again a WORM infected with PE_BOBAX.
At first I thought this was just a technique to raise the infection rate of PE_BOBAX. Now I’m realizing a new angle on this, it may also be done to avoid detection of the Infector itself (PE_BOBAX).
This is because most AV engineers would then be fooled to detect the INFECTED WORM, thus the nasty little bugger (I’m talking about PE_BOBAX here) that is carried by the WORM gets away, free to infect other files in the user’s system.
So far the most successfull in spreading is the one infected with WORM_MYTOB.