From f9805954ee581ff6c3dc2ec4bb48c7deca32ba74 Mon Sep 17 00:00:00 2001
From: Brent Murphy <56412096+bm11100@users.noreply.github.com>
Date: Fri, 28 May 2021 15:09:09 -0400
Subject: [PATCH] [New Rule] Unusual Network Connection via DllHost (#1232)

* Create defense_evasion_unusual_network_connection_via_dllhost.toml
* add timestamp override

(cherry picked from commit c457614e37bf7b6db02de84c7fa71a5620783236)
---
 ...nusual_network_connection_via_dllhost.toml | 53 +++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 rules/windows/defense_evasion_unusual_network_connection_via_dllhost.toml

diff --git a/rules/windows/defense_evasion_unusual_network_connection_via_dllhost.toml b/rules/windows/defense_evasion_unusual_network_connection_via_dllhost.toml
new file mode 100644
index 000000000..233f19cc1
--- /dev/null
+++ b/rules/windows/defense_evasion_unusual_network_connection_via_dllhost.toml
@@ -0,0 +1,53 @@
+[metadata]
+creation_date = "2021/05/28"
+maturity = "production"
+updated_date = "2021/05/28"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies unusual instances of dllhost.exe making outbound network connections. This may indicate adversarial Command
+and Control activity.
+"""
+from = "now-9m"
+index = ["winlogbeat-*", "logs-endpoint.events.*", "logs-windows.*"]
+language = "eql"
+license = "Elastic License v2"
+name = "Unusual Network Connection via DllHost"
+references = [
+    "https://www.microsoft.com/security/blog/2021/05/27/new-sophisticated-email-based-attack-from-nobelium/",
+    "https://www.volexity.com/blog/2021/05/27/suspected-apt29-operation-launches-election-fraud-themed-phishing-campaigns/",
+    "https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml",
+]
+risk_score = 47
+rule_id = "c7894234-7814-44c2-92a9-f7d851ea246a"
+severity = "medium"
+tags = ["Elastic", "Host", "Windows", "Threat Detection", "Defense Evasion"]
+timestamp_override = "event.ingested"
+type = "eql"
+
+query = '''
+sequence by host.id, process.entity_id with maxspan=1m
+  [process where event.type in ("start", "process_started") and process.name : "dllhost.exe" and process.args_count == 1]
+  [network where 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")]
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+name = "Signed Binary Proxy Execution"
+reference = "https://attack.mitre.org/techniques/T1218/"
+id = "T1218"
+
+
+[rule.threat.tactic]
+name = "Defense Evasion"
+reference = "https://attack.mitre.org/tactics/TA0005/"
+id = "TA0005"
+