Backdoor:Win32/Kelihos.A (Microsoft); W32.Waledac.B (Symantec)
Windows 2000, Windows XP, Windows Server 2003
This worm uses social engineering methods to lure users into performing certain actions that may, directly or indirectly, cause malicious routines to be performed. Specifically, it makes use of spam messages disguised as electronic greeting cards.
To get a one-glance comprehensive view of the behavior of this Worm, refer to the Threat Diagram shown below.
This worm sends out spam emails which contain links to TROJ_KELIHOS.DLR. It may also be downloaded from remote sites by other malware.
When executed, it connects to other computers infected with this worm through TCP port 80. It then gets the list of IP addresses the remote computer has logged and adds them to the list of IP addresses it connects to. It sends a list of IP addresses of infected systems once it receives remote connection via the same port.
This worm also executes with the parameter <i>/loggs99</i> to log its activities. It then saves its log file onto the infected system.
This worm may be downloaded from remote sites by other malware.
Arrival Details
This worm may be downloaded from remote site(s) by the following malware:
It may be downloaded from the following remote sites:
Installation
This worm creates the following folders:
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
Autostart Technique
This worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
SmartIndex = {malware path and file name}
Other System Modifications
This worm adds the following registry keys:
HKEY_CURRENT_USER\Software\Google
It adds the following registry entries:
HKEY_CURRENT_USER\Software\Google
ID = 50
HKEY_CURRENT_USER\Software\Google
ID2 = {random values}
HKEY_CURRENT_USER\Software\Google
ID3 = {random values}
HKEY_CURRENT_USER\Software\Google
AppID = {random characters}
Backdoor Routine
This worm opens the following port(s) where it listens for remote commands:
Other Details
This worm does the following:
Note, however, that the binaries downloaded from the link may change depending on what infected machine they are retrieved, which changes.
It sends a GET request to the server to download an encrypted data, which contains information on its spamming routine.
The email it sends has the following format:
From: {name of sender}
Subject: {subject}
Message Body:
{name of sender} {message 1} {message 2}
{message 3}
{malicious link}
Some samples bear the following details:
{name of sender}:
{subject}:
{message 1} can be any of the following:
{message 2} can be any of the following:
{message 3} can be any of the following:
{malicious link} can be any link where TROJ_KELIHOS.DLR can be downloaded.
It displays information on its activities when it is executed with the parameter /loggs99. Below is a screenshot of the said log:
Step 1
Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.
Step 3
Identify and terminate files detected as WORM_KELIHOS.SM
Step 4
Delete this registry value
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
Step 5
Delete this registry key
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
Step 6
Search and delete this folder
Step 7
Scan your computer with your Trend Micro product to delete files detected as WORM_KELIHOS.SM. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.