Connection to Commonly Abused Web Services

  1[metadata]
  2creation_date = "2020/11/04"
  3integration = ["endpoint"]
  4maturity = "production"
  5min_stack_comments = "New fields added: required_fields, related_integrations, setup"
  6min_stack_version = "8.3.0"
  7updated_date = "2023/06/22"
  8
  9[transform]
 10[[transform.osquery]]
 11label = "Osquery - Retrieve DNS Cache"
 12query = "SELECT * FROM dns_cache"
 13
 14[[transform.osquery]]
 15label = "Osquery - Retrieve All Services"
 16query = "SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services"
 17
 18[[transform.osquery]]
 19label = "Osquery - Retrieve Services Running on User Accounts"
 20query = """
 21SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services WHERE
 22NOT (user_account LIKE '%LocalSystem' OR user_account LIKE '%LocalService' OR user_account LIKE '%NetworkService' OR
 23user_account == null)
 24"""
 25
 26[[transform.osquery]]
 27label = "Osquery - Retrieve Service Unsigned Executables with Virustotal Link"
 28query = """
 29SELECT concat('https://www.virustotal.com/gui/file/', sha1) AS VtLink, name, description, start_type, status, pid,
 30services.path FROM services JOIN authenticode ON services.path = authenticode.path OR services.module_path =
 31authenticode.path JOIN hash ON services.path = hash.path WHERE authenticode.result != 'trusted'
 32"""
 33
 34
 35[rule]
 36author = ["Elastic"]
 37description = """
 38Adversaries may implement command and control (C2) communications that use common web services to hide their activity.
 39This attack technique is typically targeted at an organization and uses web services common to the victim network, which
 40allows the adversary to blend into legitimate traffic activity. These popular services are typically targeted since they
 41have most likely been used before compromise, which helps malicious traffic blend in.
 42"""
 43from = "now-9m"
 44index = ["logs-endpoint.events.*"]
 45language = "eql"
 46license = "Elastic License v2"
 47name = "Connection to Commonly Abused Web Services"
 48note = """## Triage and analysis
 49
 50### Investigating Connection to Commonly Abused Web Services
 51
 52Adversaries may use an existing, legitimate external Web service as a means for relaying data to/from a compromised system. Popular websites and social media acting as a mechanism for C2 may give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to a compromise.
 53
 54This rule looks for processes outside known legitimate program locations communicating with a list of services that can be abused for exfiltration or command and control.
 55
 56> **Note**:
 57> This investigation guide uses the [Osquery Markdown Plugin](https://www.elastic.co/guide/en/security/master/invest-guide-run-osquery.html) introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.
 58
 59#### Possible investigation steps
 60
 61- Investigate the script 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.
 62- Investigate other alerts associated with the user/host during the past 48 hours.
 63- Verify whether the digital signature exists in the executable.
 64- Identify the operation type (upload, download, tunneling, etc.).
 65- Examine the host for derived artifacts that indicate suspicious activities:
 66  - Analyze the process executable using a private sandboxed analysis system.
 67  - Observe and collect information about the following activities in both the sandbox and the alert subject host:
 68    - Attempts to contact external domains and addresses.
 69      - Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process' `process.entity_id`.
 70      - Examine the DNS cache for suspicious or anomalous entries.
 71        - $osquery_0
 72    - Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
 73    - Examine the host services for suspicious or anomalous entries.
 74      - $osquery_1
 75      - $osquery_2
 76      - $osquery_3
 77  - Retrieve the files' SHA-256 hash values using the PowerShell `Get-FileHash` cmdlet and search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
 78- Investigate potentially compromised accounts. Analysts can do this by searching for login events (for example, 4624) to the target host after the registry modification.
 79
 80### False positive analysis
 81
 82- This rule has a high chance to produce false positives because it detects communication with legitimate services. Noisy false positives can be added as exceptions.
 83
 84### Response and remediation
 85
 86- Initiate the incident response process based on the outcome of the triage.
 87- Isolate the involved host to prevent further post-compromise behavior.
 88- If the triage identified malware, search the environment for additional compromised hosts.
 89  - Implement temporary network rules, procedures, and segmentation to contain the malware.
 90  - Stop suspicious processes.
 91  - Immediately block the identified indicators of compromise (IoCs).
 92  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
 93- Remove and block malicious artifacts identified during triage.
 94- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
 95- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
 96- 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).
 97"""
 98risk_score = 21
 99rule_id = "66883649-f908-4a5b-a1e0-54090a1d3a32"
100severity = "low"
101tags = ["Domain: Endpoint", "OS: Windows", "Use Case: Threat Detection", "Tactic: Command and Control", "Resources: Investigation Guide", "Data Source: Elastic Defend"]
102timestamp_override = "event.ingested"
103type = "eql"
104
105query = '''
106network where host.os.type == "windows" and network.protocol == "dns" and
107    process.name != null and user.id not in ("S-1-5-18", "S-1-5-19", "S-1-5-20") and
108    /* Add new WebSvc domains here */
109    dns.question.name :
110    (
111        "raw.githubusercontent.*",
112        "*.pastebin.*",
113        "*drive.google.*",
114        "*docs.live.*",
115        "*api.dropboxapi.*",
116        "*dropboxusercontent.*",
117        "*onedrive.*",
118        "*4shared.*",
119        "*.file.io",
120        "*filebin.net",
121        "*slack-files.com",
122        "*ghostbin.*",
123        "*ngrok.*",
124        "*portmap.*",
125        "*serveo.net",
126        "*localtunnel.me",
127        "*pagekite.me",
128        "*localxpose.io",
129        "*notabug.org",
130        "rawcdn.githack.*",
131        "paste.nrecom.net",
132        "zerobin.net",
133        "controlc.com",
134        "requestbin.net",
135        "cdn.discordapp.com",
136        "discordapp.com",
137        "discord.com",
138        "script.google.com",
139        "script.googleusercontent.com"
140    ) and
141    /* Insert noisy false positives here */
142    not (
143      process.executable : (
144        "?:\\Program Files\\*.exe",
145        "?:\\Program Files (x86)\\*.exe",
146        "?:\\Windows\\System32\\WWAHost.exe",
147        "?:\\Windows\\System32\\smartscreen.exe",
148        "?:\\Windows\\System32\\MicrosoftEdgeCP.exe",
149        "?:\\ProgramData\\Microsoft\\Windows Defender\\Platform\\*\\MsMpEng.exe",
150        "?:\\Users\\*\\AppData\\Local\\Google\\Chrome\\Application\\chrome.exe",
151        "?:\\Users\\*\\AppData\\Local\\Programs\\Fiddler\\Fiddler.exe",
152        "?:\\Users\\*\\AppData\\Local\\Programs\\Microsoft VS Code\\Code.exe",
153        "?:\\Users\\*\\AppData\\Local\\Microsoft\\OneDrive\\OneDrive.exe",
154        "?:\\Windows\\system32\\mobsync.exe",
155        "?:\\Windows\\SysWOW64\\mobsync.exe"
156      ) or
157    
158      /* Discord App */
159      (process.name : "Discord.exe" and (process.code_signature.subject_name : "Discord Inc." and
160       process.code_signature.trusted == true) and dns.question.name : ("discord.com", "cdn.discordapp.com", "discordapp.com")
161      ) or 
162
163      /* MS Sharepoint */
164      (process.name : "Microsoft.SharePoint.exe" and (process.code_signature.subject_name : "Microsoft Corporation" and
165       process.code_signature.trusted == true) and dns.question.name : "onedrive.live.com"
166      ) or 
167
168      /* Firefox */
169      (process.name : "firefox.exe" and (process.code_signature.subject_name : "Mozilla Corporation" and
170       process.code_signature.trusted == true)
171      )
172    ) 
173'''
174
175
176[[rule.threat]]
177framework = "MITRE ATT&CK"
178[[rule.threat.technique]]
179id = "T1102"
180name = "Web Service"
181reference = "https://attack.mitre.org/techniques/T1102/"
182
183
184[rule.threat.tactic]
185id = "TA0011"
186name = "Command and Control"
187reference = "https://attack.mitre.org/tactics/TA0011/"
188[[rule.threat]]
189framework = "MITRE ATT&CK"
190[[rule.threat.technique]]
191id = "T1567"
192name = "Exfiltration Over Web Service"
193reference = "https://attack.mitre.org/techniques/T1567/"
194[[rule.threat.technique.subtechnique]]
195id = "T1567.001"
196name = "Exfiltration to Code Repository"
197reference = "https://attack.mitre.org/techniques/T1567/001/"
198
199[[rule.threat.technique.subtechnique]]
200id = "T1567.002"
201name = "Exfiltration to Cloud Storage"
202reference = "https://attack.mitre.org/techniques/T1567/002/"
203
204
205
206[rule.threat.tactic]
207id = "TA0010"
208name = "Exfiltration"
209reference = "https://attack.mitre.org/tactics/TA0010/"