PowerShell Suspicious Script with Screenshot Capabilities

 1[metadata]
 2creation_date = "2021/10/19"
 3integration = ["windows"]
 4maturity = "production"
 5updated_date = "2024/10/28"
 6min_stack_version = "8.14.0"
 7min_stack_comments = "Breaking change at 8.14.0 for the Windows Integration."
 8
 9[rule]
10author = ["Elastic"]
11description = """
12Detects PowerShell scripts that can take screenshots, which is a common feature in post-exploitation kits and remote
13access tools (RATs).
14"""
15from = "now-9m"
16index = ["winlogbeat-*", "logs-windows.powershell*"]
17language = "kuery"
18license = "Elastic License v2"
19name = "PowerShell Suspicious Script with Screenshot Capabilities"
20note = """## Triage and analysis
21
22### Investigating PowerShell Suspicious Script with Screenshot Capabilities
23
24PowerShell is one of the main tools system administrators use for automation, report routines, and other tasks, which makes it available for use in various environments and creates an attractive way for attackers to execute code.
25
26Attackers can abuse PowerShell capabilities and take screen captures of desktops to gather information over the course of an operation.
27
28#### Possible investigation steps
29
30- Examine the script content that triggered the detection; look for suspicious DLL imports, collection or exfiltration capabilities, suspicious functions, encoded or compressed data, and other potentially malicious characteristics.
31- 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.
32- Examine file or network events from the involved PowerShell process for suspicious behavior.
33- Investigate other alerts associated with the user/host during the past 48 hours.
34- Evaluate whether the user needs to use PowerShell to complete tasks.
35- Determine whether the script stores the captured data locally.
36- Investigate whether the script contains exfiltration capabilities and identify the exfiltration server.
37- Assess network data to determine if the host communicated with the exfiltration server.
38
39### False positive analysis
40
41- Regular users do not have a business justification for using scripting utilities to take screenshots, which makes false positives unlikely. In the case of authorized benign true positives (B-TPs), exceptions can be added.
42
43### Related rules
44
45- PowerShell Keylogging Script - bd2c86a0-8b61-4457-ab38-96943984e889
46
47### Response and remediation
48
49- Initiate the incident response process based on the outcome of the triage.
50- Isolate the involved hosts to prevent further post-compromise behavior.
51- Restrict PowerShell usage outside of IT and engineering business units using GPOs, AppLocker, Intune, or similar software.
52- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business systems, and web services.
53- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
54- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
55- 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).
56"""
57references = ["https://docs.microsoft.com/en-us/dotnet/api/system.drawing.graphics.copyfromscreen"]
58risk_score = 47
59rule_id = "959a7353-1129-4aa7-9084-30746b256a70"
60setup = """## Setup
61
62The 'PowerShell Script Block Logging' logging policy must be enabled.
63Steps to implement the logging policy with Advanced Audit Configuration:

1
2Steps to implement the logging policy via registry:

 1"""
 2severity = "medium"
 3tags = [
 4    "Domain: Endpoint",
 5    "OS: Windows",
 6    "Use Case: Threat Detection",
 7    "Tactic: Collection",
 8    "Resources: Investigation Guide",
 9    "Data Source: PowerShell Logs",
10]
11timestamp_override = "event.ingested"
12type = "query"
13
14query = '''
15event.category:process and host.os.type:windows and
16  powershell.file.script_block_text : (
17    CopyFromScreen and
18    ("System.Drawing.Bitmap" or "Drawing.Bitmap")
19  ) and not user.id : "S-1-5-18"
20'''
21
22
23[[rule.threat]]
24framework = "MITRE ATT&CK"
25[[rule.threat.technique]]
26id = "T1113"
27name = "Screen Capture"
28reference = "https://attack.mitre.org/techniques/T1113/"
29
30
31[rule.threat.tactic]
32id = "TA0009"
33name = "Collection"
34reference = "https://attack.mitre.org/tactics/TA0009/"
35[[rule.threat]]
36framework = "MITRE ATT&CK"
37[[rule.threat.technique]]
38id = "T1059"
39name = "Command and Scripting Interpreter"
40reference = "https://attack.mitre.org/techniques/T1059/"
41[[rule.threat.technique.subtechnique]]
42id = "T1059.001"
43name = "PowerShell"
44reference = "https://attack.mitre.org/techniques/T1059/001/"
45
46
47
48[rule.threat.tactic]
49id = "TA0002"
50name = "Execution"
51reference = "https://attack.mitre.org/tactics/TA0002/"