A program or set of programs which hides itself by subverting or evading the computer's security mechanisms, then allows remote users to secretly control the computer's operating system.
Disinfection & Removal
Allow F-Secure Anti-Virus (FSAV) to disinfect the relevant files. For more general information on disinfection, please see Removal Instructions.
If a suspicious hidden file is detected and FSAV does not immediately remove the file, there are several actions you can perform by manually selecting one of the displayed option:
- If you don't want to do anything about the hidden item, select "None" as the action
- If you don't want to be notified about the file in the future, select "Exclude" as the action
- If you are sure the item is not part of a normal program, you can rename it by selecting "Rename" as the action. This will prevent the hidden program from starting in the future. You should use the "Rename" action very carefully, because renaming important files may break the computer.
Sending A Sample to F-Secure (Advanced users)
Since hidden items are often related to malware, we ask that you consider sending us a sample of the hidden files. Since the files are hidden, you might not be able to access them directly. To access the files, you might need to do one of the following:
- Start your computer in safe mode. In safe mode, the files may become visible. To do so, you may need to refer to the relevant Microsoft documentation for your specific operating system version.
- Rename the files. After renaming the files and restarting the computer, the files may become visible. In some cases, the computer must be started in safe mode after renaming for it to be successful.
- Reboot your system using Windows Recovery Console. The files should be accessible when using the Recovery Console.
Alternatively, users may use the following instructions:
Once obtained, the sample can be forwarded to our Security Labs via the Sample Analysis System (SAS):
Manual Repair of the MBR
Caution: Manual disinfection of the MBR is only recommended for advanced users.
Microsoft provides tools to replace an infected MBR with a copy of the original, clean MBR. To do so:
- Boot into the Recovery Console.
- Depending on the operating system in question, run the appropriate command on all
- On Windows XP, run:fixmbr
- On Windows 7, run:bootrec
Note: For further information on use of the 'fixmbr' command, please refer to the relevant Microsoft documentation.
When searching our Virus Descriptions database for a specific program (e.g., Rootkit:W32/Example.A), you may be directed to this page if the overview below sufficiently describes the program.
Alternatively, you may be directed to this page if no description matching that specific query is currently available. You can submit a sample of the suspect file to our Response Lab for further analysis via:
A rootkit is usually a standalone software component that attempts to hide processes,files, registry data and network connections. Though rootkits are not malicious in themselves, numerous malware use a rootkit component to facilitate their malicious routines and to protect the malware from detection/deletion.
A rootkit can be either user-mode or kernel-mode. A user-mode rootkit is usually dropped as a DLL file, which the malware then loads to all running processes in order for the rootkit to run; a kernel-mode rootkit is usually dropped as a driver file, which is then loaded as part of the kernel, or the operating system's core components. In rare cases, the rootkit doesn't need any external files to operate.
Examples of pure rootkits are Hacker Defender and FU. Some spyware and adware programs (e.g., EliteToolbar, ProAgent and Probot SE) also use rootkit techiques, as well as some trojans (e.g., Haxdoor, Berbew/Padodor and Feutel/Hupigon), and worms.
Hidden Items or Processes
Hidden processes, files and applications detected on the system are displayed as suspicious items. The presence of these items can indicate the following:
- A normal, non-malicious application might be hidden for some reason OR
- Malware (a stealth virus, rootkit or spyware) may be hiding on the computer
There are many malicious and non-malicious reasons why items can be hidden on the computer:
- XCP Digital Rights Management (DRM) software: The copy-protection software included on some music CD's hides files and processes. While the files are not malicious, there are security risks involved with them.
- Backdoor:W32/Haxdoor: Note that this backdoor hides important system files, which are not malicious themselves.
- Apropos: This is a family of spyware that hides files and processes.
MBR Rootkit (boot image)
A detection name that uses the format "Rootkit.mbr.[variant] (boot image)" indicates the possible presence of a hidden component or program that affects the Master Boot Record (MBR), a dedicated area of a storage device - such as a hard drive or a floppy disk - that contains critical information for starting the main operating system (OS).