SMB (Windows File Sharing) Activity to the Internet

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SMB (Windows File Sharing) Activity to the Internet

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This rule detects network events that may indicate the use of Windows file sharing (also called SMB or CIFS) traffic to the Internet. SMB is commonly used within networks to share files, printers, and other system resources amongst trusted systems. It should almost never be directly exposed to the Internet, as it is frequently targeted and exploited by threat actors as an initial access or back-door vector or for data exfiltration.

Rule type: query

Rule indices:

  • auditbeat-*
  • filebeat-*
  • packetbeat-*
  • logs-endpoint.events.*

Severity: high

Risk score: 73

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Elastic
  • Host
  • Network
  • Threat Detection
  • Initial Access
  • Host

Version: 10

Rule authors:

  • Elastic

Rule license: Elastic License v2

Rule query

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event.category:(network or network_traffic) and network.transport:tcp and (destination.port:(139 or 445) or event.dataset:zeek.smb) and
  source.ip:(
    10.0.0.0/8 or
    172.16.0.0/12 or
    192.168.0.0/16
  ) and
  not destination.ip:(
    10.0.0.0/8 or
    127.0.0.0/8 or
    169.254.0.0/16 or
    172.16.0.0/12 or
    192.0.0.0/24 or
    192.0.0.0/29 or
    192.0.0.8/32 or
    192.0.0.9/32 or
    192.0.0.10/32 or
    192.0.0.170/32 or
    192.0.0.171/32 or
    192.0.2.0/24 or
    192.31.196.0/24 or
    192.52.193.0/24 or
    192.168.0.0/16 or
    192.88.99.0/24 or
    224.0.0.0/4 or
    100.64.0.0/10 or
    192.175.48.0/24 or
    198.18.0.0/15 or
    198.51.100.0/24 or
    203.0.113.0/24 or
    240.0.0.0/4 or
    "::1" or
    "FE80::/10" or
    "FF00::/8"
  )

Framework: MITRE ATT&CKTM