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F-Secure Malware Information Pages: Small.DAM
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| Radar Alert |
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| Level 2 |
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Summary
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| Small.DAM, a variant of Small, is a Trojan that arrives on the system as attachment file to spam emails. Small.DAM loads a malicious service named "wincom32" in the affected machine. |
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Disinfection
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Automatic Disinfection
Usually standalone malware (backdoors, worms, trojans, etc.) is automatically removed by F-Secure Anti-Virus (FSAV) starting from version 5.40. Malware files get automatically renamed by FSAV, so they can not be started any more. In some rare cases, when automatic disinfection is not possible, a user can select disinfection action by him/herself to make FSAV rename or delete an infected file. In some special cases, it is recommended to use specific disinfection tools provided by F-Secure. They can be downloaded from our ftp site:
ftp://ftp.f-secure.com/anti-virus/tools/
F-Secure Anti-Virus can be purchased from our webshop or from our authorized distributors. A trial version F-Secure Anti-Virus, limited to 30 days, can be downloaded from our website:
http://www.f-secure.com/download-purchase/
All the latest versions of FSAV can download anti-virus database updates automatically. However, these updates can be also downloaded and installed manually from our web or ftp sites:
http://www.f-secure.com/download-purchase/updates.shtml
Manual Disinfection
To manually disinfect standalone malware (backdoors, worms, trojans, etc.) it is usually enough to delete all infected files from a computer and to restart it. Active malware files are usually locked by the operating system so different disinfection approaches are required for different operating systems.
Please note that manual disinfection is a risky process, so it is recommended only for advanced users.
If Windows 95, 98, and ME operating systems are used, it is recommended to restart a computer from a bootable system diskette and to delete an infected file from command prompt. For example, if a malicious file named ABC.EXE is located in the Windows folder, it is usually enough to type the following command at the command prompt:
DEL C:\WINDOWS\ABC.EXE
and to press Enter. After that, an infected file will be gone. If Windows NT, 2000 or XP are used, a malicious file has to be renamed with a different extension (for example .VIR) and then a system has to be restarted. After restarting, a renamed malicious file will no longer be active and it can be easily to delete it manually.
Malware Disinfection Tools
F-Secure provides disinfection tools for certain malware. These tools can be downloaded from this webpage:
http://www.f-secure.com/download-purchase/tools.shtml
ftp://ftp.f-secure.com/anti-virus/tools/
Windows System Restore Issues
If Windows ME or XP are used, it is recommended to disable System Restore features of these operating systems to prevent a computer from re-infection by an already removed malware. The fact is that System Restore feature of these operating systems might save an infected file into the special folder and copy it back to a hard drive every time it has been renamed or deleted by F-Secure Anti-Virus or by a user. Instructions on how to disable System Restore features are here:
Windows ME:
http://www.f-secure.com/v-descs/sfc_dis.shtml
Windows XP:
http://www.f-secure.com/v-descs/sfc_dis1.shtml
It is recommended to re-enable System Restore features after disinfection in order to restore stable system configuration, if any crash or incompatibility issue occurs in the future.
Failed Disinfection
In some cases, F-Secure Anti-Virus might not disinfect a system automatically. In this case, please visit our Support pages:
http://support.f-secure.com/enu/home/virusproblem/howtoclean/ |
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Detailed Description
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Small.DAM arrives on the system as an attachment file to spam e-mails.
Here's a sample of an e-mail:
It may use any of the following strings as its Subject:
- 230 dead as storm batters Europe.
- A killer at 11, he's free at 21 and...
- British Muslims Genocide
- Naked teens attack home director.
- U.S. Secretary of State Condoleezza Rice has kicked German Chancellor Angela Merkel
Attachments may be any of the following filenames:
- Full Clip.exe
- Full Story.exe
- Read More.exe
- Video.exe
Small.DAM drops the following files upon execution:
- %SysDir%\wincom32.sys - Kernel mode driver component
- %SysDir%\peers.ini - Initialization file component
It also installs itself as a service with the name "wincom32" by creating the following registry keys:
- [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wincom32]
- [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_WINCOM32]
The kernel mode driver is an advanced payload injector. It carries a user-mode PE executable file and when the driver executes, it changes the services.exe process context and allocates new memory for the payload. It then copies the PE executable from kernel memory to the address space of services.exe and prepares the image for execution. Finally, it queues an Asynchronous Procedure Call (APC) for services.exe to execute the payload in its context.
This is the injected PE executable file trojan downloader in action and affected machines exhibits sending UDP packets with source port 4000 to IP addresses and destination ports taken from the decoded initialization file's "peers" section. The initialization file also maintains a "blacklist" section.
Additional information can be found from our weblog. |
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Detection
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F-Secure Anti-Virus detects this malware with the following updates: [FSAV_Database_Version] Version = 2007-01-15_01.
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F-Secure Corporation |
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Last Modified: January 19, 2007
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