Backdoor.Win32.AckCmd

Parent class: TrojWare

Trojans are malicious programs that perform actions which are not authorized by the user: they delete, block, modify or copy data, and they disrupt the performance of computers or computer networks. Unlike viruses and worms, the threats that fall into this category are unable to make copies of themselves or self-replicate. Trojans are classified according to the type of action they perform on an infected computer.

Class: Backdoor

Backdoors are designed to give malicious users remote control over an infected computer. In terms of functionality, Backdoors are similar to many administration systems designed and distributed by software developers. These types of malicious programs make it possible to do anything the author wants on the infected computer: send and receive files, launch files or delete them, display messages, delete data, reboot the computer, etc. The programs in this category are often used in order to unite a group of victim computers and form a botnet or zombie network. This gives malicious users centralized control over an army of infected computers which can then be used for criminal purposes. There is also a group of Backdoors which are capable of spreading via networks and infecting other computers as Net-Worms do. The difference is that such Backdoors do not spread automatically (as Net-Worms do), but only upon a special “command” from the malicious user that controls them.

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Platform: Win32

Win32 is an API on Windows NT-based operating systems (Windows XP, Windows 7, etc.) that supports execution of 32-bit applications. One of the most widespread programming platforms in the world.

Description

Technical Details

This Troajn program can be used for remote administration of the victim machine. It has both a client and a server component.

The server component is written in Microsoft Visual C++. It is 28672 bytes in size, and is not packed in any way. The client component is also written in Microsoft Visual C++, and it 32768 bytes in size. It is not packed in any way.

Payload

The remote malicious user launches the client component on his/ her machine. This makes it possible to send commands to the server component which is installed on the victim machine. The malicious user has to give the address of the victim machine.

The program contains the following strings:

The server component makes it possible for the remote malicious user to open the command line on the victim machine and execute commands via the command line on the victim machine.

The interesting feature about this backdoor is that it only uses ACK packets. This means that a standard connection is not established; rather, data will be transmitted directly using ACK packets. This makes it possible for the Trojan to bypass some firewalls.

The backdoor does not have any replication routine.

Removal instructions

1. Use Task Manager to terminate the Trojan process.
2. Delete the original backdoor file (its location on the victim machine will depend on how the program originally penetrated the victim machine).
3. Update your antivirus databases, and perform a full scan of the computer (download a trial version of Kaspersky Anti-Virus).

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