WORM_COREFLOOD.A
Windows 2000, XP, Server 2003
Threat Type: Worm
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
Propagates via peer-to-peer networks
Upon execution, it terminates EXPLORER.EXE and restarts the process with its code injected in it. It then attempts to resolve the host to any certain servers. Once a user opens a browser, it will perform a HTTP POST request containing system information. It expects to receive backdoor commands from the server. The server replies with certain commands such as to download, execute, and save the downloaded copy of itself.
It scans the network for random IP addresses to search for target systems. It then attempts to drop and execute the copy of itself to target IP addresses.
It downloads a non-malicious component from its server. It then uses this downloaded file to unpack the archive file it downloads from the server. The said archive file contains an updated copy of this worm.
It monitors certain applications. It logs user keystrokes when affected users visit websites. It logs the status of its installation to the affected system and to all the network shares it tried to infect to certain files. It may also steal data from HTTPS sessions.
This worm may be unknowingly downloaded by a user while visiting malicious websites.
TECHNICAL DETAILS
Varies
Varies
PE
Yes
30 Oct 2010
Compromises system security, Steals information
Arrival Details
This worm may be unknowingly downloaded by a user while visiting malicious websites.
It may be downloaded from the following remote sites:
- http://savupdate.{BLOCKED}evalidate.net/ctfup32.rar
- http://health.{BLOCKED}plus.net/ctfup32.rar
Installation
This worm drops the following files:
- %User Temp%\~~{random number}.tmp - also detected as BKDR_OFICLA.AI
- %System%\{random file name}.dat - encrypted data
- %System%\{random file name}.ocx - copy of itself
(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)
Autostart Technique
This worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CLASSES_ROOT\CLSID\{random CLSID}
(Default) = {random registry value}
HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
(Default) = %System%\{random file name}.ocx
HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
ThreadingModel = Apartment
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
ShellIconOverlayIdentifiers\{random key}
(Default) = {random CLSID}
Other Details
Based on analysis of the codes, it has the following capabilities:
Backdoor Routines
Upon execution, it terminates EXPLORER.EXE and restarts the process with its code injected in it. It then attempts to resolve the host to any of the following servers:
- http://{BLOCKED}ate.licensevalidate.net
- http://{BLOCKED}s.hostfarmville.net
Once a user opens a browser, it will perform a HTTP POST request with the following parameters containing system information:
- http://{malware server}/index.php/r={parameter}&i=&v={version}&os={operating system}&s=&h=&d={parameter}&b={parameter}&u={parameter}&k={parameter}&m={parameter}&panic={parameter}&ie={parameter}&input={parameter}&c={country of affected system}&l={parameter}
It will then expect to receive backdoor commands from the server.
As of writing, the server replies with commands that does the following:
- Assign a unique ID for the bot
- Move a file named "c:\myservice.log" - not present in the system
- Download, execute, and save the file downloaded from the website http://savupdate.{BLOCKED}evalidate.net/login.php as %User Temp%\tmsfoload.exe. Trend Micro detects this executable file as WORM_COREFLOOD.A. As of writing, the downloaded file is an updated copy of itself.
Propagation via Network Shares
- It scans the network for random IP addresses to search for target systems.
- It then attempts to drop and execute the following copy of itself to target IP addresses:
- %Windows%\System\ctfmnt.exe
Download Routine
It downloads a non-malicious component file named rar.exe from its server. It will then use this downloaded file to unpack the next file it will download from the server, ctfup32.rar, which is an archive file containing an updated copy of the malware.
Initially, the malware will save all the downloaded files to the %User Temp% folder. Afterwards, it will install the contents of the archive ctfup32.rar to the %Windows%\System folder.
Information Theft
It monitors certain applications such as the following:
- Firefox
- Opera
- Skype
It logs user keystrokes when affected users visit Web sites with the following strings:
- answer
- challenge
- clave
- codigo
- firma
- identifica
- memorable
- parol
- passphras
- password
- secret
- secur
- segur
Other Details
- %User Temp%\tlmlg1.log
- %User Temp%\tlmlg2.log
- Steal data from HTTPS sessions.
- Read these component files, which are currently not found on systems: ie.dat, input.dat, other.dat, panic.dat.
SOLUTION
8.900
7.580.05
30 Oct 2010
10/30/2010 12:00:00 AM
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
Restart in Safe Mode
Step 3
Delete the created random CLSID 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 4
Search and delete this file
- %System%\{random file name}.dat
- %User Temp%\ctfup32.rar
- %User Temp%\rar.exe
- %User Temp%\tlmlg1.log
- %User Temp%\tlmlg2.log
Step 5
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_COREFLOOD.A. 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.
Step 6
Scan your computer with your Trend Micro product to delete files detected as WORM_COREFLOOD.A. 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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