PWS:Win32/Zbot.J is a password stealing trojan that has been observed in the wild targeting Bank of America websites. Win32/Zbot also contains backdoor functionality that allows unauthorized access and control of an affected machine.
Win32/Zbot has been observed being distributed in the wild attached to e-mail that spoofs UPS (United Parcel Service of America).
Installation
When executed, PWS:Win32/Zbot.J copies itself with a variable file name to the System directory, for example:
<system folder>\sdra64.exe
It modifies the registry to execute this copy at each Windows start:
Sets value: "userinit"
With data: "<system folder>\userinit.exe,<system folder>\<malware filename>,"
To subkey: HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
For example:
Sets value: "userinit"
With data: "<system folder>\userinit.exe,<system folder>\sdra64.exe"
To subkey: HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
Many Zbot variants utilize code injection in order to hinder detection and removal. When PWS:Win32/Zbot.J executes, it may inject code into the running process 'winlogon.exe', which in turn injects code into other running processes.
Payload
Steals Sensitive Information
The Zbot family of malware is used to obtain sensitive information from the affected system, such as:
- Trusted Web site certificates
- Cached Web browser passwords
- Cookies
Many Zbot variants specifically target the websites of Bank of America.
Variants of Zbot may also parse e-mail and FTP traffic in order to obtain e-mail addresses and FTP login details.
Backdoor Functionality
Zbot can be instructed to perform a host of actions by a remote attacker, including the following:
- Renaming itself
- Obtaining certificates and other stolen information
- Blocking URLs
- Downloading and executing arbitrary files
- Establishing a Socks proxy
Contacts Remote Site for Instruction/Downloads and Executes Arbitrary Files
After installation, Zbot contacts a remote site to download additional instructions and/or arbitrary files to execute.
Additional Information
Zbot variants may make the following registry modifications:
Sets value: "UID"
With data: "avm<machine specific ID>"
To subkey: HKLM\Software\Microsoft\Windows NT\CurrentVersion\Network
Sets value: "ParseAutoexec"
With data: "1"
To subkey: HKCU\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
Sets value: "Start Page"
With data: ""
To subkey: HKCU\software\microsoft\internet explorer\main
Analysis by Matt McCormack