Trojan-Dropper:W32/Hoaxer.B

This malware drops and installs multiple files in the system. The cumulative effect of the malware is to produce a fake infection warning, which aims to frighten the user into purchasing a rogue antivirus program. InstallationThe malware installs a variety of files on the system. These files are all detected as Trojan-Downloader.Win32.Hoaxer.a:

• %programfiles%\PCHealthCenter\0.exe
• %programfiles%\PCHealthCenter\1.exe
• %programfiles%\PCHealthCenter\2.exe
• %programfiles%\PCHealthCenter\3.exe
• %programfiles%\PCHealthCenter\4.exe
• %programfiles%\PCHealthCenter\5.exe
• %programfiles%\PCHealthCenter\7.exe

These files are all image files used by the sc.html file:

• %programfiles%\PCHealthCenter\0.gif
• %programfiles%\PCHealthCenter\1.gif
• %programfiles%\PCHealthCenter\2.gif
• %programfiles%\PCHealthCenter\3.gif

This file is the fake Windows Security Center warning:

• %programfiles%\PCHealthCenter\sc.html

These icons are for links to pornography sites:

• %programfiles%\PCHealthCenter\1.ico
• %programfiles%\PCHealthCenter\2.ico

In addition to icons for links, the malware also adds actual links to the megafreeporn website:

• [random number][random number]%desktop%\QUALITY PORN.url
• [random number][random number]%desktop%\BEST ZOO PORN.url

These files are essentially duplicates of files which have been previously installed:

• c:\x - same file as %programfiles%\PCHealthCenter\7.ex
• %windir%\system32\YUR[random number].exe - same file as %programfiles%\PCHealthCenter\1.exe
• [random number]%windir%\system32\YUR[random number].exe - same file as %programfiles%\PCHealthCenter\2.exe
• [random number]%windir%\system32\YUR[random number].exe - same file as %programfiles%\PCHealthCenter\3.exe
• [random number][random number]%windir%\system32\YUR[random number].exe - same file as %programfiles%\PCHealthCenter\4.exe
• [random number][random number]%windir%\system32\1.ico - same as %programfiles%\PCHealthCenter\1.ico
• [random number][random number]%windir%\system32\2.ico - same as %programfiles%\PCHealthCenter\2.ico

Finally, the malware installs a file which is detected as Fraudtool:W32/SpywarePreventer.A:

• http://first-reason.com/data/x7/[...]/0000005378.exe

Registry

The malware also makes a number of registry changes in order to display the installed files. Sample registry values would be:

• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR1.exe = C:\Windows\system32\YUR1.exe
• HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR1.exe = C:\Windows\system32\YUR1.exe
• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR2.exe = C:\Windows\system32\YUR2.exe
• HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR2.exe = C:\Windows\system32\YUR2.exe
• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR3.exe = C:\Windows\system32\YUR3.exe
• HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR3.exe = C:\Windows\system32\YUR3.exe
• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR4.exe = C:\Windows\system32\YUR4.exe
• HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR4.exe = C:\Windows\system32\YUR4.exe

Execution

Upon execution, the malware will immediately display the sc.html file, which appears to be a Windows Security Center warning that the system is infected.

The user is asked if they would like to scan and remove the (supposed) threats detected, which is the recommended option. If the user clicks on the "Yes" option in the dialog box, the malware will open this link in the browser:

• http://scanner.vav-x-scanner.com/34/?advid=[...]5378&dsbndbinj&

The page opened contains the product that the malware is promoting.

File System Changes

Create these directories:

• %programfiles%\PCHealthCenter

Process Changes

Creates these processes:

• %programfiles%\PCHealthCenter\0.exe
• %programfiles%\PCHealthCenter\1.exe
• %programfiles%\PCHealthCenter\2.exe
• %programfiles%\PCHealthCenter\3.exe
• %programfiles%\PCHealthCenter\4.exe
• %programfiles%\PCHealthCenter\5.exe
• %programfiles%\PCHealthCenter\7.exe

Registry Modifications

Sets these values:

• HKCU\SOFTWARE\Microsoft\Windows VRSIN = 1221124757
• HKCU\SOFTWARE\Microsoft\Windows AIM = 0000000000005378
• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR.exe = C:\Windows\system32\YUR.exe
• HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR.exe = C:\Windows\system32\YUR.exe
• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR.exe = C:\Windows\system32\YUR.exe
• HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR.exe = C:\Windows\system32\YUR.exe
• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR.exe = C:\Windows\system32\YUR.exe
• HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR.exe = C:\Windows\system32\YUR.exe
• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR.exe = C:\Windows\system32\YUR.exe
• HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run \YUR.exe = C:\Windows\system32\YUR.exe