Potential Encoded PowerShell Patterns In CommandLine

calendar Oct 18, 2023 · attack.defense_evasion attack.t1027 attack.execution attack.t1059.001  ·
Share on: linkedin copy

Detects specific combinations of encoding methods in PowerShell via the commandline

Sigma rule (View on GitHub)

 1title: Potential Encoded PowerShell Patterns In CommandLine
 2id: cdf05894-89e7-4ead-b2b0-0a5f97a90f2f
 3related:
 4    - id: 5b572dcf-254b-425c-a8c5-d9af6bea35a6
 5      type: similar
 6status: test
 7description: Detects specific combinations of encoding methods in PowerShell via the commandline
 8references:
 9    - https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=65
10author: Teymur Kheirkhabarov (idea), Vasiliy Burov (rule), oscd.community, Tim Shelton
11date: 2020/10/11
12modified: 2023/01/26
13tags:
14    - attack.defense_evasion
15    - attack.t1027
16    - attack.execution
17    - attack.t1059.001
18logsource:
19    category: process_creation
20    product: windows
21detection:
22    selection_img:
23        - Image|endswith:
24              - '\powershell.exe'
25              - '\pwsh.exe'
26        - OriginalFileName:
27              - 'PowerShell.EXE'
28              - 'pwsh.dll'
29    selection_to_1:
30        CommandLine|contains:
31            - 'ToInt'
32            - 'ToDecimal'
33            - 'ToByte'
34            - 'ToUint'
35            - 'ToSingle'
36            - 'ToSByte'
37    selection_to_2:
38        CommandLine|contains:
39            - 'ToChar'
40            - 'ToString'
41            - 'String'
42    selection_gen_1:
43        CommandLine|contains|all:
44            - 'char'
45            - 'join'
46    selection_gen_2:
47        CommandLine|contains|all:
48            - 'split'
49            - 'join'
50    condition: selection_img and (all of selection_to_* or 1 of selection_gen_*)
51falsepositives:
52    - Unknown
53level: low

References

  • Hunting for PowerShell Abuse

    PowerShell is the favorit tool of IT guys, who are responsible for administration of Windows infrastructures. It allows them to manage differen services of the operating system and automate almost anything. But along with administrators, PowerShell also is liked by attackers and malware authors. The reason PowerShell is so attractive for adversaries is quite obvious: it has been included in essentially every Windows operating system by default for a decade, provides access to Windows API, and is rarely constrained, thus allowing adversaries to perform different tasks without risking being blocked. ttackers can use PowerShell to direct the execution of a local script, retrieve and execute remote resources using various network protocols, encode payloads passed via the command line, or load PowerShell into other processes. Because of so prevalence of PowerShell among adversaries for Threat Hunters it is very important to be able to detect malicious uses of PowerShell and defend against it. In the presentation author is going to demostrate an approaches for detection of PowerShell abuses based on different event sources like native Windows logging capabilities as well as usage of additional tools, like Sysmon or EDR solutions. How to collect traces of using PowerShell, how to filter out false positives, and how to find evidence of malicious uses among the remaining after filtering volume of events — all these questions will be answered in the talk for present and future threat hunters.


    Read More

Related rules

to-top