WORM_PALEVO.AAA
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Worm
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
It opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system. It executes commands from a remote malicious user, effectively compromising the affected system.
TECHNICAL DETAILS
Arrival Details
This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
Installation
This worm drops the following copies of itself into the affected system:
- %System Root%\RECYCLER\{Random SID}\mwau.exe
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It drops the following non-malicious file:
- %System Root%\RECYCLER\{Random SID}\Desktop.ini
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It creates the following folders:
- %System Root%\RECYCLER\{Random SID}
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It adds the following mutexes to ensure that only one of its copies runs at any one time:
- mmm_fejh__frg65fx
It injects itself into the following processes as part of its memory residency routine:
- EXPLORER.EXE
Autostart Technique
This worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Taskman = "%System Root%\RECYCLER\{Random SID}\mwau.exe"
Propagation
This worm creates the following folders in all removable drives:
- {Drive Letter}:\winamp_cache_0001
It drops the following copy(ies) of itself in all removable drives:
- {Drive Letter}:\winamp_cache_0001\ehthumbs.exe
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
The said .INF file contains the following strings:
;ýv?ÁtÐ?gN?ªm????E?Ð?ç?ëÁ?üX?õ(sÐë???a??Øä,Á
[autorun
:jmp0
open=winamp_cache_0001\ehthumbs.exe
:nop
icon=%SystemRoot%\system32\SHELL32.dll,4
;à???k?Ô|?I)ñ???Ô?O-òXeJ??????_?
action=Open folder to view files using Windows Explorer
;?W???E?ñ????Êoë?f??ìJY[L?Q??Öõ??ý?Ò?)????
shell\\\open\\\command=winamp_cache_0001/ehthumbs.exe
shell\\explore\\\command=winamp_cache_0001/ehthumbs.exe
useautoplay=1
[AutoRun]
;ÖOBmù>de??(Üd??æddÁd??àëdOÚ!Ã?mÚr?al?aÙ?X?r??Ì?/?&??v?Tâìy?í?ôl???Ég
:GOTO NUL
Backdoor Routine
This worm opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.
It executes the following commands from a remote malicious user:
- Performs DDoS Attack
- Download files
- Start and stop MSN spreader
- Start and stop Removable drives spreader
- Spread via P2P applications
It connects to the following URL(s) to send and receive commands from a remote malicious user:
- server1.{BLOCKED}q.com
- server1.{BLOCKED}aq.com
- server1.{BLOCKED}aaaaq.com
SOLUTION
Step 1
For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.
Step 2
Identify and delete files detected as WORM_PALEVO.AAA using the Recovery Console
Step 3
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.
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- Taskman = "%System Root%\RECYCLER\{Random SID}\mwau.exe"
- Taskman = "%System Root%\RECYCLER\{Random SID}\mwau.exe"
Step 4
Search and delete these folders
Step 5
Search and delete AUTORUN.INF files created by WORM_PALEVO.AAA that contain these strings
Step 6
Scan your computer with your Trend Micro product to delete files detected as WORM_PALEVO.AAA. 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.
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