Unsigned DLL Side-Loading from a Suspicious Folder

  1[metadata]
  2creation_date = "2022/11/22"
  3integration = ["endpoint"]
  4maturity = "production"
  5updated_date = "2024/05/21"
  6
  7[rule]
  8author = ["Elastic"]
  9description = """
 10Identifies a Windows trusted program running from locations often abused by adversaries to masquerade as a trusted
 11program and loading a recently dropped DLL. This behavior may indicate an attempt to evade defenses via side-loading a
 12malicious DLL within the memory space of a signed processes.
 13"""
 14from = "now-9m"
 15index = ["logs-endpoint.events.library-*"]
 16language = "eql"
 17license = "Elastic License v2"
 18name = "Unsigned DLL Side-Loading from a Suspicious Folder"
 19risk_score = 47
 20rule_id = "ca98c7cf-a56e-4057-a4e8-39603f7f0389"
 21setup = """## Setup
 22
 23If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
 24events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
 25Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
 26`event.ingested` to @timestamp.
 27For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
 28"""
 29severity = "medium"
 30tags = [
 31    "Domain: Endpoint",
 32    "OS: Windows",
 33    "Use Case: Threat Detection",
 34    "Tactic: Defense Evasion",
 35    "Data Source: Elastic Defend",
 36]
 37timestamp_override = "event.ingested"
 38type = "eql"
 39
 40query = '''
 41library where host.os.type == "windows" and
 42
 43 process.code_signature.trusted == true and 
 44 
 45 (dll.Ext.relative_file_creation_time <= 500 or dll.Ext.relative_file_name_modify_time <= 500) and 
 46 
 47  not dll.code_signature.status : ("trusted", "errorExpired", "errorCode_endpoint*", "errorChaining") and 
 48  
 49      /* Suspicious Paths */
 50      dll.path : ("?:\\PerfLogs\\*.dll",
 51                  "?:\\Users\\*\\Pictures\\*.dll",
 52                  "?:\\Users\\*\\Music\\*.dll",
 53                  "?:\\Users\\Public\\*.dll",
 54                  "?:\\Users\\*\\Documents\\*.dll",
 55                  "?:\\Windows\\Tasks\\*.dll",
 56                  "?:\\Windows\\System32\\Tasks\\*.dll",
 57                  "?:\\Intel\\*.dll",
 58                  "?:\\AMD\\Temp\\*.dll",
 59                  "?:\\Windows\\AppReadiness\\*.dll",
 60                  "?:\\Windows\\ServiceState\\*.dll",
 61                  "?:\\Windows\\security\\*.dll",
 62		  "?:\\Windows\\System\\*.dll",
 63                  "?:\\Windows\\IdentityCRL\\*.dll",
 64                  "?:\\Windows\\Branding\\*.dll",
 65                  "?:\\Windows\\csc\\*.dll",
 66                  "?:\\Windows\\DigitalLocker\\*.dll",
 67                  "?:\\Windows\\en-US\\*.dll",
 68                  "?:\\Windows\\wlansvc\\*.dll",
 69                  "?:\\Windows\\Prefetch\\*.dll",
 70                  "?:\\Windows\\Fonts\\*.dll",
 71                  "?:\\Windows\\diagnostics\\*.dll",
 72                  "?:\\Windows\\TAPI\\*.dll",
 73                  "?:\\Windows\\INF\\*.dll",
 74                  "?:\\windows\\tracing\\*.dll",
 75                  "?:\\windows\\IME\\*.dll",
 76                  "?:\\Windows\\Performance\\*.dll",
 77                  "?:\\windows\\intel\\*.dll",
 78                  "?:\\windows\\ms\\*.dll",
 79                  "?:\\Windows\\dot3svc\\*.dll",
 80                  "?:\\Windows\\ServiceProfiles\\*.dll",
 81                  "?:\\Windows\\panther\\*.dll",
 82                  "?:\\Windows\\RemotePackages\\*.dll",
 83                  "?:\\Windows\\OCR\\*.dll",
 84                  "?:\\Windows\\appcompat\\*.dll",
 85                  "?:\\Windows\\apppatch\\*.dll",
 86                  "?:\\Windows\\addins\\*.dll",
 87                  "?:\\Windows\\Setup\\*.dll",
 88                  "?:\\Windows\\Help\\*.dll",
 89                  "?:\\Windows\\SKB\\*.dll",
 90                  "?:\\Windows\\Vss\\*.dll",
 91                  "?:\\Windows\\Web\\*.dll",
 92                  "?:\\Windows\\servicing\\*.dll",
 93                  "?:\\Windows\\CbsTemp\\*.dll",
 94                  "?:\\Windows\\Logs\\*.dll",
 95                  "?:\\Windows\\WaaS\\*.dll",
 96                  "?:\\Windows\\twain_32\\*.dll",
 97                  "?:\\Windows\\ShellExperiences\\*.dll",
 98                  "?:\\Windows\\ShellComponents\\*.dll",
 99                  "?:\\Windows\\PLA\\*.dll",
100                  "?:\\Windows\\Migration\\*.dll",
101                  "?:\\Windows\\debug\\*.dll",
102                  "?:\\Windows\\Cursors\\*.dll",
103                  "?:\\Windows\\Containers\\*.dll",
104                  "?:\\Windows\\Boot\\*.dll",
105                  "?:\\Windows\\bcastdvr\\*.dll",
106                  "?:\\Windows\\TextInput\\*.dll",
107                  "?:\\Windows\\schemas\\*.dll",
108                  "?:\\Windows\\SchCache\\*.dll",
109                  "?:\\Windows\\Resources\\*.dll",
110                  "?:\\Windows\\rescache\\*.dll",
111                  "?:\\Windows\\Provisioning\\*.dll",
112                  "?:\\Windows\\PrintDialog\\*.dll",
113                  "?:\\Windows\\PolicyDefinitions\\*.dll",
114                  "?:\\Windows\\media\\*.dll",
115                  "?:\\Windows\\Globalization\\*.dll",
116                  "?:\\Windows\\L2Schemas\\*.dll",
117                  "?:\\Windows\\LiveKernelReports\\*.dll",
118                  "?:\\Windows\\ModemLogs\\*.dll",
119                  "?:\\Windows\\ImmersiveControlPanel\\*.dll",
120                  "?:\\$Recycle.Bin\\*.dll") and 
121	 
122	 /* DLL loaded from the process.executable current directory */
123	 endswith~(substring(dll.path, 0, length(dll.path) - (length(dll.name) + 1)), substring(process.executable, 0, length(process.executable) - (length(process.name) + 1)))
124'''
125
126
127[[rule.threat]]
128framework = "MITRE ATT&CK"
129[[rule.threat.technique]]
130id = "T1036"
131name = "Masquerading"
132reference = "https://attack.mitre.org/techniques/T1036/"
133[[rule.threat.technique.subtechnique]]
134id = "T1036.001"
135name = "Invalid Code Signature"
136reference = "https://attack.mitre.org/techniques/T1036/001/"
137
138
139[[rule.threat.technique]]
140id = "T1574"
141name = "Hijack Execution Flow"
142reference = "https://attack.mitre.org/techniques/T1574/"
143[[rule.threat.technique.subtechnique]]
144id = "T1574.002"
145name = "DLL Side-Loading"
146reference = "https://attack.mitre.org/techniques/T1574/002/"
147
148
149
150[rule.threat.tactic]
151id = "TA0005"
152name = "Defense Evasion"
153reference = "https://attack.mitre.org/tactics/TA0005/"