Query: Outbound C2 pattern associated with File/Path Exclusions
Matching passage: T1564.012 File/Path Exclusions. Tactics: stealth. Description: Adversaries may attempt to hide their file-based artifacts by writing them to specific folders or file names excluded from antivirus (AV) scanning and other defensive capabilities. AV and other file-based scanners often include exclusions to optimize performance as well as ease installation and legitimate use of applications. These exclusions may be contextual (e.g., scans are only initiated in response to specific triggering events/alerts), but are also often hardcoded strings referencing specific folders and/or files assumed to be trusted and legitimate.(Citation: Microsoft File Folder Exclusions) Adversaries may abuse these exclusions to hide their file-based artifacts. For example, rather than tampering with tool settings to add a new exclusion (i.e., [Disable or Modify Tools](https://attack.mitre.org/techniques/T1685)), adversaries may drop their file-based payloads in default or otherwise well-known exclusions. Adversaries may also use [Security Software Discovery](https://attack.mitre.org/techniques/T1518/001) and other [Discovery](https://attack.mitre.org/tactics/TA0007)/[Reconnaissance](https://attack.mitre.org/tactics/TA0043) activities to both discover and verify existing exclusions in a victim environment.
Near-miss passage: T1564.014 Extended Attributes. Tactics: stealth. Description: Adversaries may abuse extended attributes (xattrs) on macOS and Linux to hide their malicious data in order to evade detection. Extended attributes are key-value pairs of file and directory metadata used by both macOS and Linux. They are not visible through standard tools like `Finder`, `ls`, or `cat` and require utilities such as `xattr` (macOS) or `getfattr` (Linux) for inspection. Operating systems and applications use xattrs for tagging, integrity checks, and access control. On Linux, xattrs are organized into namespaces such as `user.` (user permissions), `trusted.` (root permissions), `security.`, and `system.`, each with specific permissions. On macOS, xattrs are flat strings without namespace prefixes, commonly prefixed with `com.apple.*` (e.g., `com.apple.quarantine`, `com.apple.metadata:_kMDItemUserTags`) and used by system features like Gatekeeper and Spotlight.(Citation: Establishing persistence using extended attributes on Linux) An adversary may leverage xattrs by embedding a second-stage payload into the extended attribute of a legitimate file. On macOS, a payload can be embedded into a custom attribute using the `xattr` command. A separate loader can retrieve the attribute with `xattr -p`, decode the content, and execute it using a scripting interpreter. On Linux, an adversary may use `setfattr` to write a payload into the `user.` namespace of a legitimate file. A loader script can later extract the payload with `getfattr --only-values`, decode it, and execute it using bash or another interpreter. In both cases, because the primary file content remains unchanged, security tools and integrity checks that do not inspect extended attributes will observe the original file hash, allowing the malicious payload to evade detection.(Citation: Low GroupIB xattrs nov 2024)