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System Binary Symlink to Suspicious Location

This rule detects the creation of a symbolic link from a system binary to a suspicious and writable location. This activity may indicate an attacker's attempt to evade detection by behavioral rules that depend on predefined process parent/child relationships. By executing the symlinked variant of a binary instead of the original, the attacker aims to bypass these rules. Through the new_terms rule type, this rule can identify uncommon parent processes that may indicate the presence of a malicious symlink.

Rule type: new_terms
Rule indices:

  • logs-endpoint.events.process*

Rule Severity: low
Risk Score: 21
Runs every:
Searches indices from: now-9m
Maximum alerts per execution: ?
References:

Tags:

  • Domain: Endpoint
  • OS: Linux
  • Use Case: Threat Detection
  • Tactic: Defense Evasion
  • Data Source: Elastic Defend

Version: ?
Rule authors:

  • Elastic

Rule license: Elastic License v2

host.os.type:linux and event.category:process and event.type:start and event.action:exec and process.parent.executable:* and
(process.name:ln or process.name:busybox and process.args:ln or process.name:cp and process.args:--symbolic-link) and
process.args:(
  (
    /bin/* or /lib/* or /lib64/* or /sbin/* or /usr/bin/* or /usr/lib/* or /usr/lib64/* or /usr/local/bin/* or
    /usr/local/lib/* or /usr/local/lib64/* or /usr/local/sbin/* or /usr/sbin/*
  ) and (
    /*/.* or /dev/shm/* or /home/* or /root/* or /tmp/* or /var/tmp/*
  ) and
  not (/usr/bin/coreutils or /tmp/mkinitcpio* or /var/tmp/dracut* or /var/tmp/mkinitramfs*)
)

Framework: MITRE ATT&CK