PE_YAZ.A
Virus:Win32/Yaz.A (Microsoft); Virus.Win32.Yaz.a (Kaspersky); BehavesLike.Win32.Malware.spi (mx-v) (Sunbelt); Win32.Yaz.A (FSecure)
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
Threat Type: File infector
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This file infector arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
TECHNICAL DETAILS
330,240 bytes
EXE
Yes
03 Feb 2012
Arrival Details
This file infector 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 file infector creates the following folders:
- %Application Data%\VMware
(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)
Autostart Technique
This file infector adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
yazzz = "%User Temp%\ctxmon.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
atitool = "%User Profile%\Application Data\pwrwin.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
atitool = "%User Profile%\Application Data\pwrwin.exe"
Other System Modifications
This file infector deletes the following files:
- %User Startup%\icwstart.lnk
(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Session Manager\SFC
ProgramFilesDir = "%Program Files%"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Session Manager\SFC
CommonFilesDir = "%Program Files%\Common Files"
Dropping Routine
This file infector drops the following files:
- %User Profile%\Application Data\pwrwin.exe
(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)
This report is generated via an automated analysis system.
SOLUTION
9.200
Step 1
Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.
Step 2
Restart in Safe Mode
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
- yazzz = "%User Temp%\ctxmon.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- atitool = "%User Profile%\Application Data\pwrwin.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- atitool = "%User Profile%\Application Data\pwrwin.exe"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\SFC
- ProgramFilesDir = "%Program Files%"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\SFC
- CommonFilesDir = "%Program Files%\Common Files"
Step 4
Search and delete this file
- %User Profile%\Application Data\pwrwin.exe
Step 5
Search and delete this folder
- %Application Data%\VMware
Step 6
Restart in normal mode and scan your computer with your Trend Micro product for files detected as PE_YAZ.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 7
Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.
- %User Startup%\icwstart.lnk
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