Suspicious XOR Encoded PowerShell Command Line - PowerShell

calendar Oct 28, 2023 · attack.execution attack.t1059.001  ·
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Detects suspicious powershell process which includes bxor command, alternative obfuscation method to b64 encoded commands.

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 1title: Suspicious XOR Encoded PowerShell Command Line - PowerShell
 2id: 812837bb-b17f-45e9-8bd0-0ec35d2e3bd6
 3status: test
 4description: Detects suspicious powershell process which includes bxor command, alternative obfuscation method to b64 encoded commands.
 5references:
 6    - https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=46
 7author: Teymur Kheirkhabarov, Harish Segar (rule)
 8date: 2020/06/29
 9modified: 2023/10/27
10tags:
11    - attack.execution
12    - attack.t1059.001
13logsource:
14    product: windows
15    category: ps_classic_start
16detection:
17    selection:
18        Data|contains: 'HostName=ConsoleHost'
19    filter:
20        Data|contains:
21            - 'bxor'
22            - 'char'
23            - 'join'
24    condition: selection and filter
25falsepositives:
26    - Unknown
27level: medium

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.


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