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Worm.Win32.Vobfus.afzf

Class Worm
Platform Win32
Family Vobfus
Full name Worm.Win32.Vobfus.afzf
Examples 1365A5E5BFC7DE770D0CC67799F31630
5A9C7343C72054E001967D365DFE6EFF
4AFA443FC5432B5EB565991C4823A516
18A74F8AA88D401C5318EA978BC89EE9
2C27C38A73BA9F73149B0B0ADBFB848A
Updated at 2023-10-21 12:21:02
Tactics &
techniques MITRE*

TA0005 Defense Evasion

The adversary is trying to avoid being detected.


Defense Evasion consists of techniques that adversaries use to avoid detection throughout their compromise. Techniques used for defense evasion include uninstalling/disabling security software or obfuscating/encrypting data and scripts. Adversaries also leverage and abuse trusted processes to hide and masquerade their malware. Other tactics’ techniques are cross-listed here when those techniques include the added benefit of subverting defenses.


T1564.001 Hide Artifacts: Hidden Files and Directories

Adversaries may set files and directories to be hidden to evade detection mechanisms. To prevent normal users from accidentally changing special files on a system, most operating systems have the concept of a ‘hidden’ file. These files don’t show up when a user browses the file system with a GUI or when using normal commands on the command line. Users must explicitly ask to show the hidden files either via a series of Graphical User Interface (GUI) prompts or with command line switches (dir /a for Windows and ls –a for Linux and macOS).

On Linux and Mac, users can mark specific files as hidden simply by putting a “.” as the first character in the file or folder name (Citation: Sofacy Komplex Trojan) (Citation: Antiquated Mac Malware). Files and folders that start with a period, ‘.’, are by default hidden from being viewed in the Finder application and standard command-line utilities like “ls”. Users must specifically change settings to have these files viewable.

Files on macOS can also be marked with the UF_HIDDEN flag which prevents them from being seen in Finder.app, but still allows them to be seen in Terminal.app (Citation: WireLurker). On Windows, users can mark specific files as hidden by using the attrib.exe binary. Many applications create these hidden files and folders to store information so that it doesn’t clutter up the user’s workspace. For example, SSH utilities create a .ssh folder that’s hidden and contains the user’s known hosts and keys.

Adversaries can use this to their advantage to hide files and folders anywhere on the system and evading a typical user or system analysis that does not incorporate investigation of hidden files.
* © 2024 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation.
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