Trojan-Downloader.Java.OpenConnection.er

Removal Instructions

If your computer has not been protected with anti-virus software and has been infected with malware, you will need to take the following actions to delete this:

  1. Delete the original trojan file (its location on the infected computer will depend on how it got onto the computer).
  2. Delete the following file:
    %USERPROFILE%\<rnd>.exe

  3. Update Sun Java JRE and JDK to the latest versions.
  4. Clear the Temporary Internet Files directory which may contain infected files (How to delete infected files in the Temporary Internet Files folder?).
  5. Run a full Kaspersky Antivirus scan with updated antivirus databases (download trial version).



MD5: B128448CE2DEC747EC806A47800F7100
SHA1: 82961301732E8AF889BDB1B7E50197C8B433BC5B

Payload

The malicious JAR-archive contains the following files:

bingo\chugun.class (365 bytes)
bingo\dipler.class (1394 bytes)
bingo\efir.class (17766 bytes; detected by Kaspersky Antivirus as "Trojan-Downloader.Java.OpenConnection.er ")
bingo\haskalu.class (2532 bytes) bingo\kipoltyrew.class (856 bytes) Meta-inf\Manifest.mf (71 bytes)

This set of classes is an implementation of the Java-applet (main applet class - "efir"), using the vulnerability CVE-2010-0840 to download files from the internet to the infected computer. This vulnerability is as a result of an incorrect validation when implementing the preferred methods in JRE (Java Runtime Environment), which allows the attacker to implement an arbitrary code using an object that has been modified in a certain way as a sub-class of the proxy class. In this case, the "getValue()" inheritance method is implemented for the "Expression" proxy class. A similar inheritance cannot be implemented directly from the malicious Java-applet class which is a subclass of the non-privileged "Applet" class.


The applet is launched from an infected HTML-page using the "<APPLET>" tag, for which an encrypted link to download the file is transferred in the "kdwidth" parameter. The link is deciphered using the "fipoluty" function implemented in the "efir" class. When decoding, the following mapping is used for input and output symbols:


Input symbols:

xTc/8:G1RqgymtFz_S?nuJHkpP=DBaeOj2&7Q%Mh5bXdK0vf4E-YCisAwV9rI.3oZl6LN#UW

Output symbols:
0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ/.:_-?&=%#

After launching, the trojan checks the name of the OS installed on the infected computer. If the OS is not Windows, the trojan shuts down. Otherwise, the file is downloaded from the link obtained and saved as
%USERPROFILE%\<rnd>.exe

where <rnd> is a random fractional decimal between 0 and 1.


After successfully downloading the file, it is then launched for execution.


The trojan also sets the value of the "java.net.useSystemProxies" parameter to "true".

Technical Details

A trojan program that downloads files from the Internet without the user's knowledge and launches them. It is a JAR-archive containing a set of Java-classes (class-files). 18043 bytes.