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Startup or Run Key Registry Modification

Identifies run key or startup key registry modifications. In order to survive reboots and other system interrupts, attackers will modify run keys within the registry or leverage startup folder items as a form of persistence.

Rule type: eql

Rule indices:

  • logs-endpoint.events.*

Severity: low

Risk score: 21

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References: None

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Persistence

Version: 101

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guide

Adversaries may achieve persistence by referencing a program with a registry run key. Adding an entry to the run keys
in the registry will cause the program referenced to be executed when a user logs in. These programs will executed
under the context of the user and will have the account's permissions. This rule looks for this behavior by monitoring
a range of registry run keys.

  • Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files
    for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
  • Investigate other alerts associated with the user/host during the past 48 hours.
  • Validate the activity is not related to planned patches, updates, network administrator activity, or legitimate
    software installations.
  • Assess whether this behavior is prevalent in the environment by looking for similar occurrences across hosts.
  • Retrieve the process executable and determine if it is malicious:
    • Use a private sandboxed malware analysis system to perform analysis.
      • Observe and collect information about the following activities:
        • Attempts to contact external domains and addresses.
        • File and registry access, modification, and creation activities.
        • Service creation and launch activities.
        • Scheduled task creation.
    • Use the PowerShell Get-FileHash cmdlet to get the files' SHA-256 hash values.
      • Search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
  • There is a high possibility of benign legitimate programs being added to registry run keys. This activity could be
    based on new software installations, patches, or any kind of network administrator related activity. Before undertaking
    further investigation, verify that this activity is not benign.
  • Suspicious Startup Shell Folder Modification - c8b150f0-0164-475b-a75e-74b47800a9ff
  • Persistent Scripts in the Startup Directory - f7c4dc5a-a58d-491d-9f14-9b66507121c0
  • Startup Folder Persistence via Unsigned Process - 2fba96c0-ade5-4bce-b92f-a5df2509da3f
  • Startup Persistence by a Suspicious Process - 440e2db4-bc7f-4c96-a068-65b78da59bde
  • Initiate the incident response process based on the outcome of the triage.
  • Isolate the involved host to prevent further post-compromise behavior.
  • If the triage identified malware, search the environment for additional compromised hosts.
    • Implement temporary network rules, procedures, and segmentation to contain the malware.
    • Stop suspicious processes.
    • Immediately block the identified indicators of compromise (IoCs).
    • Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that
      attackers could use to reinfect the system.
  • Remove and block malicious artifacts identified during triage.
  • Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are
    identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business
    systems, and web services.
  • Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and
    malware components.
  • Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
  • Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the
    mean time to respond (MTTR).

Rule query

registry where registry.data.strings != null and
 registry.path : (
     /* Machine Hive */
     "HKLM\\Software\\Microsoft\\Windows\\CurrentVersion\\Run\\*",
     "HKLM\\Software\\Microsoft\\Windows\\CurrentVersion\\RunOnce\\*",
     "HKLM\\Software\\Microsoft\\Windows\\CurrentVersion\\RunOnceEx\\*",
     "HKLM\\Software\\Microsoft\\Windows\\CurrentVersion\\Policies\\Explorer\\Run\\*",
     "HKLM\\Software\\Microsoft\\Windows NT\\CurrentVersion\\Winlogon\\Shell\\*",
     /* Users Hive */
     "HKEY_USERS\\*\\Software\\Microsoft\\Windows\\CurrentVersion\\Run\\*",
     "HKEY_USERS\\*\\Software\\Microsoft\\Windows\\CurrentVersion\\RunOnce\\*",
     "HKEY_USERS\\*\\Software\\Microsoft\\Windows\\CurrentVersion\\RunOnceEx\\*",
     "HKEY_USERS\\*\\Software\\Microsoft\\Windows\\CurrentVersion\\Policies\\Explorer\\Run\\*",
     "HKEY_USERS\\*\\Software\\Microsoft\\Windows NT\\CurrentVersion\\Winlogon\\Shell\\*"
     ) and
  /* add common legitimate changes without being too restrictive as this is one of the most abused AESPs */
  not registry.data.strings : "ctfmon.exe /n" and
  not (registry.value : "Application Restart #*" and process.name : "csrss.exe") and
  user.id not in ("S-1-5-18", "S-1-5-19", "S-1-5-20") and
  not registry.data.strings : ("?:\\Program Files\\*.exe", "?:\\Program Files (x86)\\*.exe") and
  not process.executable : ("?:\\Windows\\System32\\msiexec.exe", "?:\\Windows\\SysWOW64\\msiexec.exe") and
  not (process.name : "OneDriveSetup.exe" and
       registry.value : ("Delete Cached Standalone Update Binary", "Delete Cached Update Binary", "amd64", "Uninstall *") and
       registry.data.strings : "?:\\Windows\\system32\\cmd.exe /q /c * \"?:\\Users\\*\\AppData\\Local\\Microsoft\\OneDrive\\*\"")

Framework: MITRE ATT&CKTM