PWS:Win32/Zbot.SZ is a detection for a password stealer and remote access trojan. The trojan is installed by other malware.
Installation
When run, PWS:Win32/Zbot.SZ drops a modified copy of itself as a randomly named file:
%APPDATA%\<random letters>\<random letters>.exe
For example:
c:\Documents and Settings\Administrator\Application Data\dopyq\ruro.exe
The registry is modified to run the dropped malware at Windows start.
Sets value: "{GUID of Windows volume}"
With data: "%APPDATA%\<random letters>\<random letters>.exe"
To subkey: HKCU\Software\Microsoft\Windows\Currentversion\Run
The malware injects codes into the address space of the following processes to mask its presence:
taskhost.exe
taskeng.exe
wscntfy.exe
ctfmon.exe
rdpclip.exe
explorer.exe
Additionally, PWS:Win32/Zbot.SZ hooks the following Windows system APIs to aid in the capture of sensitive data:
PWS:Win32/Zbot.SZ hooks the following additional APIs to support FireFox:
PR_OpenTCPSocket
PR_Close
PR_Read
PR_Write
Payload
Steal sensitive data
PWS:Win32/Zbot.SZ hooks APIs used by Internet Explorer and Mozilla Firefox to steal login credentials when a user visits certain websites. A configuration file may be downloaded from a remote server (for example, "dairanet.cn") and captured data will be sent to a predefined FTP or e-mail server.
The trojan collects FTP credentials (IP, port, username, and passwords) from the following FTP software:
FlashFXP
Total Commander
ws_ftp
FileZilla
FAR/FAR2
winscp
FTP Commander
CoreFTP
SmartFTP
PWS:Win32/Zbot.SZ steals the following sensitive information from the affected computer:
certificates
IE cookies
cache passwords
The trojan also logs keystrokes and gets a snapshot of the infected system.
Lowers web browser security
PWS:Win32/Zbot.SZ lowers Internet Explorer web browser security settings by modifying registry data.
Disables phishing filtering:
Sets value: “Enabled”
With data: "0"
Sets value: "EnabledV8”
With data: "0"
In subkey: HKCU\Software\Microsoft\Internet Explorer\PhishingFilter
Disables clearing Internet Explorer browser cookies:
Sets value: "CleanCookies"
With data: "0"
In subkey: HKCU\Software\Microsoft\Internet Explorer\Privacy
Disables Internet Explorer Internet zone security settings
Set value: "1609"
With data: "0"
In subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\0
Sets value: "1406"
With data: "0"
In subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\1
Sets value: "1609"
With data: "0"
In subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\2
Sets value: "1406"
With data: "0"
In subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3
Sets value: "1406"
With data: "0"
In subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\4
Allows remote access and control
PWS:Win32/Zbot.SZ allows varying degrees of remote access and control, depending on certain configuration data. The trojan could perform, and is not limited to, any of the following actions:
reboot/shut down affected computer
uninstall/update Zbot
enable/disable HTTP injection
get current path
search/remove files
log off
execute a program
steal Internet Explorer browser cookies
steal certificates
block/unblock URLs
set Internet Explorer home page
steal FTP credentials (details above)
steal credentials stored by Macromedia Flash Player by parsing "flashplayer.cab" with SOL (Flash Local Shared Object File) files located at “%APPDATA%\Macromedia\Flash Player”.
Additional Information
PWS:Win32/Zbot.SZ appends the following headers when invoking the hooked APIs "HttpSendRequestA", "HttpSendRequestExW" and "HttpSendRequestExA":
Accept-Encoding: identity
TE:
If-Modified-Since:
Analysis by Rodel Finones