Unusual Network Connection via DllHost

Last updated 5 months ago on 2025-08-28

Created 5 years ago on 2021-05-28

About

Identifies unusual instances of dllhost.exe making outbound network connections. This may indicate adversarial Command and Control activity.

Tags

Domain: EndpointOS: WindowsUse Case: Threat DetectionTactic: Defense EvasionData Source: Elastic DefendData Source: SysmonData Source: SentinelOneLanguage: eql

Severity

medium

Risk Score

MITRE ATT&CK™

Defense Evasion (TA0005)(external, opens in a new tab or window)

↳ System Binary Proxy Execution (T1218)(external, opens in a new tab or window)

License

Elastic License v2(external, opens in a new tab or window)

Definition

Rule Type

Event Correlation Rule

Integration Pack

Prebuilt Security Detection Rules

Index Patterns

winlogbeat-*logs-endpoint.events.process-*logs-endpoint.events.network-*logs-windows.sysmon_operational-*logs-sentinel_one_cloud_funnel.*

Related Integrations

endpoint(external, opens in a new tab or window)

windows(external, opens in a new tab or window)

sentinel_one_cloud_funnel(external, opens in a new tab or window)

Query

✄𐘗text code block:
✄𐘗sequence by host.id, process.entity_id with maxspan=1m
  [process where host.os.type == "windows" and event.type == "start" and process.name : "dllhost.exe" and process.args_count == 1]
  [network where host.os.type == "windows" and process.name : "dllhost.exe" and
   not cidrmatch(destination.ip, "10.0.0.0/8", "127.0.0.0/8", "169.254.0.0/16", "172.16.0.0/12", "192.0.0.0/24",
    "192.0.0.0/29", "192.0.0.8/32", "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32", "192.0.0.171/32", "192.0.2.0/24",
    "192.31.196.0/24", "192.52.193.0/24", "192.168.0.0/16", "192.88.99.0/24", "224.0.0.0/4", "100.64.0.0/10",
    "192.175.48.0/24", "198.18.0.0/15", "198.51.100.0/24", "203.0.113.0/24", "240.0.0.0/4", "::1", "FE80::/10",
    "FF00::/8")]

Install detection rules in Elastic Security

Detect Unusual Network Connection via DllHost in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(external, opens in a new tab or window).