BKDR_YAYIH.AB
Trojan:Win32/Yayih.A (Microsoft)
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Backdoor
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
Dropped by other malware
This backdoor may be dropped by other malware.
It executes commands from a remote malicious user, effectively compromising the affected system.
TECHNICAL DETAILS
23.040 bytes
EXE
Yes
05 Mar 2012
Connects to URLs/IPs
Arrival Details
This backdoor may be dropped by other malware.
Installation
This backdoor drops the following copies of itself into the affected system:
- %Program Files%\Common Files\{malware filename}.exe
(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)
It adds the following mutexes to ensure that only one of its copies runs at any one time:
- abcdef
Autostart Technique
This backdoor adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
common = "{malware path and file name}"
Backdoor Routine
This backdoor executes the following commands from a remote malicious user:
- Create files
- Execute command shell
- Terminate itself
It connects to the following URL(s) to send and receive commands from a remote malicious user:
- {BLOCKED}nuser.ISAsecret.com
Other Details
This backdoor drops the following file(s)/component(s):
- %Application Data%\aumLib.ini
(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)
NOTES:
It sends system information such as use rname, IP address, and OS version to the following URL:
- http://domainuser.ISAsecret.com/bbs/info.asp
SOLUTION
9.200
8.818.01
05 Mar 2012
8.819.00
06 Mar 2012
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 terminate files detected as BKDR_YAYIH.AB
- If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
- If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.
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\CurrentVersion\Run
- common = "{malware path and filename}"
- common = "{malware path and filename}"
Step 4
Search and delete this file
- %Application Data%\aumLib.ini
Step 5
Scan your computer with your Trend Micro product to delete files detected as BKDR_YAYIH.AB. 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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