Malware Information

Malware name Worm.Sohanad.BM Type Worm Affected platform Win32 Media-Type application/executable MD5 checksum CDA8CA0C3811CDB6F59924C2F2CD738C Static file yes Filesize 268,800 Bytes Alias names (also known as) Sophos Mal/Generic-A McAfee W32/Yahlover.worm.gen.c Side effects Downloads files Drops a file Lowers security settings Registry modification Propagation Local network

Description:

It copies itself to the following locations:
• %SYSDIR%\RVHOST.exe
• %WINDIR%\RVHOST.exe



The following file is created:

– %WINDIR%\Tasks\At1.job File is a scheduled task that runs the malware at predefined times.



It tries to download a file:

– The location is the following:
• http://nhatquanglan2.0catch.com/**********
It is saved on the local hard drive under: %SYSDIR%\setting.ini

The following registry keys are added in order to run the processes after reboot:

– [HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
• Yahoo Messengger="%SYSDIR%\RVHOST.exe"

– [HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
• Shell="Explorer.exe RVHOST.exe"



The following registry keys are added:

– [HKLM\SYSTEM\ControlSet001\Services\Schedule]
• AtTaskMaxHours=dword:00000000

– [HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\
WorkgroupCrawler\Shares]
• shared="%all shared folders%\New Folder.exe"



The following registry keys are changed:

Various Explorer settings:
– [HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
Old value:
• NofolderOptions=%user defined settings%
New value:
• NofolderOptions=dword:00000001

Disable Regedit and Task Manager:
– [HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System]
Old value:
• DisableTaskMgr=%user defined settings%
• DisableRegistryTools=%user defined settings%
New value:
• DisableTaskMgr=dword:00000001
• DisableRegistryTools=dword:00000001


It is spreading via Messenger. The characteristics are described below:

– Yahoo Messenger


To:
All entries in the contact list.


Message
The sent message looks like one of the following:

• E may, vao day coi co con nho nay ngon lam http://nhattruongquang.**********.com

• Vao day nghe bai nay di ban http://nhattruongquang.**********.com

• Biet tin gi chua, vao day coi di http://nhattruongquang.**********.com

• Trang Web nay coi cung hay, vao coi thu di http://nhattruongquang.**********.com

• Toi di lang thang lan trong bong toi buot gia, ve dau khi da mat em roi? Ve dau khi bao nhieu mo mong gio da vo tan... Ve dau toi biet di ve dau? http://nhattruongquang.**********.com

• Khoc cho nho thuong voi trong long, khoc cho noi sau nhe nhu khong. Bao nhieu yeu thuong nhung ngay qua da tan theo khoi may bay that xa... http://nhattruongquang.**********.com

• Tha nguoi dung noi se yeu minh toi mai thoi thi gio day toi se vui hon. Gio nguoi lac loi buoc chan ve noi xa xoi, cay dang chi rieng minh toi... http://nhattruongquang.**********.com

• Loi em noi cho tinh chung ta, nhu doan cuoi trong cuon phim buon. Nguoi da den nhu la giac mo roi ra di cho anh bat ngo... http://nhattruongquang.**********.com

• Tra lai em niem vui khi duoc gan ben em, tra lai em loi yeu thuong em dem, tra lai em niem tin thang nam qua ta dap xay. Gio day chi la nhung ky niem buon...http://nhattruongquang.**********.com


The received message may look like the following:



In order to ensure its propagation the malware attemps to connect to other machines as described below.

It drops a copy of itself to the following network share:
• %all shared folders%\New Folder.exe