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F-Secure Spyware Information Pages: Apropos

[Summary] | [Detailed Description]

Name : Apropos
Alias:ContextPlus, Adintelligence.AproposToolbar, Trojan.Win32.Crypt.t, PeopleOnPage

Apropos uses highly sophisticated stealth techniques to avoid detection.

The spyware collects the browsing habits of users and system information and sends it back to ContextPlus servers. Targeted pop-up advertisements are displayed while browsing the Web.
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Detailed Description
PeopleOnPage produces the Apropos family of spyware.

It uses the same ContextPlus engine as the public software POP!, made by PeopleOnPage. However, the Apropos branch uses a silent installer and rootkit techniques to hide itself from detection. When the client connects to the server, the name Apropos is used as the client name.

ContextPlus gathers an extensive amount of information from the user's computer. The application tracks which software is installed, what web sites are visited, and the user's browsing behavior. Each installation is given a unique ID, which is sent to the ContextPlus server to request a pop-up advertisement.

Rootkit Details

Apropos contains a kernel-mode rootkit that allows it to hide files, directories, registry keys, and processes. The rootkit is implemented by a kernel-mode driver which starts automatically early in the boot process. When the files and registry keys have been hidden, no user-mode process is allowed to access them.

The hidden items can be found with F-Secure BlackLight which can be download from:

Apropos installs itself into a randomly named directory under the Program Files folder.

Additional, it installs one randomly named executable file (.EXE) into the Windows\System32 folder and one randomly named driver (.SYS) into the Windows\System32\Drivers folder.

The following two log files generated by BlackLight illustrate this behavior:

In addition to the randomly named files, Apropos uses several statically named files that reside in the installation directory, such as ace.dll, data.bin and WinGenerics.dll. Also, the log files and cache files are easy to recognize.

Hiding Technique
The kernel-mode driver patches the kernel at a very deep level. Important data structures and several Native API functions implemented by the kernel are modified. Specifically, the following functions are patched:

  • NtCreateKey
  • NtOpenKey
  • NtEnumerateKey
  • IoCreateFile
  • NtQueryDirectoryFile
  • NtQuerySystemInformation

The operating system uses these functions to gain access to, and information about, files, directories, registry keys, and processes.


  1. Perform a BlackLight scan and select "rename" for hidden *.exe, *.sys, and *.dll files.
  2. Reboot the computer in safe mode by pressing "F8" on boot. See Microsoft for detailed instructions.
  3. When the system is running in safe mode and you have logged on, reboot back into normal mode. (Rebooting back and forth from safe mode seems unnecessary but is crucial for the renaming operation to work.)
  4. Scan the computer with "Perform a full computer check" using F-Secure Internet Security or F-Secure Client Security.

Additional Note
Apropos is not associated with Apropos Technologies, Inc (NASDAQ: APRS).
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F-Secure Corporation

Last Modified: January 01, 2006