File-Share — CraftedSignal Threat Feedhttps://feed.craftedsignal.io/tags/file-share/Trending threats, MITRE ATT&CK coverage, and detection metadata — refreshed continuously.Hugoenhello@craftedsignal.iohello@craftedsignal.ioWed, 03 Jan 2024 14:00:00 +0000Remote Execution via File Shareshttps://feed.craftedsignal.io/briefs/2024-01-remote-execution-via-file-shares/Wed, 03 Jan 2024 14:00:00 +0000hello@craftedsignal.iohttps://feed.craftedsignal.io/briefs/2024-01-remote-execution-via-file-shares/This rule identifies the execution of a file that was created by the virtual system process, potentially indicating lateral movement via network file shares in Windows environments.This detection identifies lateral movement via network file shares by detecting the execution of a file that was recently created by the virtual system process (PID 4), commonly associated with file share operations. Adversaries may leverage network shares to distribute malicious payloads or tools across the network to compromise additional hosts. This technique allows attackers to execute code remotely, expanding their foothold within the environment. The rule focuses on Windows systems and monitors for newly created executable files (e.g., .exe, .scr, .pif, .com) that are then executed. Exceptions are made for known legitimate software vendors and specific file paths to reduce false positives.

Attack Chain

  1. An attacker gains initial access to a system within the network.
  2. The attacker uploads a malicious executable (e.g., malware, custom tool) to a network file share. The file creation event is attributed to PID 4.
  3. A user or automated process on a remote system accesses the file share.
  4. The malicious executable is copied or accessed from the network share onto the remote system.
  5. The user, either intentionally or through deception, executes the malicious executable.
  6. The executed file initiates malicious activities on the remote system.
  7. The attacker achieves code execution on the remote system.
  8. The attacker uses this foothold for further lateral movement, data exfiltration, or other malicious objectives.

Impact

Successful exploitation through remote execution via file shares can lead to widespread compromise across the network. Attackers can gain unauthorized access to sensitive data, install backdoors, or deploy ransomware. The impact ranges from data breaches and financial losses to significant disruption of business operations. The severity of the impact depends on the attacker’s objectives and the extent of their lateral movement within the environment.

Recommendation

  • Deploy the provided Sigma rule to your SIEM to detect suspicious executions of files created by PID 4 on Windows systems.
  • Review and restrict write access to network shares to minimize the risk of unauthorized file uploads.
  • Monitor file creation events (event.type in (“creation”, “change”)) on network shares for unusual activity using file integrity monitoring tools.
  • Investigate any alerts generated by the Sigma rule by examining the process execution chain and associated network connections.
  • Enrich process creation events (category: process_creation) with code signature information to validate the legitimacy of executed files.
  • Use osquery to retrieve the files’ SHA-256 hash values using the PowerShell Get-FileHash cmdlet and search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
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