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Detectionhightest

Suspicious Obfuscated PowerShell Code

Detects suspicious UTF16 and base64 encoded and often obfuscated PowerShell code often used in command lines

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Florian Roth (Nextron Systems)Created Mon Jul 11Updated Tue Feb 148d01b53f-456f-48ee-90f6-bc28e67d4e35windows
Log Source
WindowsProcess Creation
ProductWindows← raw: windows
CategoryProcess Creation← raw: process_creation

Events generated when a new process is spawned on the system. Covers command-line arguments, parent/child relationships, and process metadata.

Detection Logic
Detection Logic1 selector
detection:
    selection:
        CommandLine|contains:
            #  -bxor 0x
            - 'IAAtAGIAeABvAHIAIAAwAHgA'
            - 'AALQBiAHgAbwByACAAMAB4A'
            - 'gAC0AYgB4AG8AcgAgADAAeA'
            # .Invoke() |
            - 'AC4ASQBuAHYAbwBrAGUAKAApACAAfAAg'
            - 'AuAEkAbgB2AG8AawBlACgAKQAgAHwAI'
            - 'ALgBJAG4AdgBvAGsAZQAoACkAIAB8AC'
            # {1}{0}" -f
            # {0}{3}" -f
            # {2}{0}" -f
            - 'AHsAMQB9AHsAMAB9ACIAIAAtAGYAI'
            - 'B7ADEAfQB7ADAAfQAiACAALQBmAC'
            - 'AewAxAH0AewAwAH0AIgAgAC0AZgAg'
            - 'AHsAMAB9AHsAMwB9ACIAIAAtAGYAI'
            - 'B7ADAAfQB7ADMAfQAiACAALQBmAC'
            - 'AewAwAH0AewAzAH0AIgAgAC0AZgAg'
            - 'AHsAMgB9AHsAMAB9ACIAIAAtAGYAI'
            - 'B7ADIAfQB7ADAAfQAiACAALQBmAC'
            - 'AewAyAH0AewAwAH0AIgAgAC0AZgAg'
            # {1}{0}' -f
            # {0}{3}' -f
            # {2}{0}' -f
            - 'AHsAMQB9AHsAMAB9ACcAIAAtAGYAI'
            - 'B7ADEAfQB7ADAAfQAnACAALQBmAC'
            - 'AewAxAH0AewAwAH0AJwAgAC0AZgAg'
            - 'AHsAMAB9AHsAMwB9ACcAIAAtAGYAI'
            - 'B7ADAAfQB7ADMAfQAnACAALQBmAC'
            - 'AewAwAH0AewAzAH0AJwAgAC0AZgAg'
            - 'AHsAMgB9AHsAMAB9ACcAIAAtAGYAI'
            - 'B7ADIAfQB7ADAAfQAnACAALQBmAC'
            - 'AewAyAH0AewAwAH0AJwAgAC0AZgAg'
    condition: selection
False Positives
Unknown

False positive likelihood has not been assessed. Additional context may be needed during triage.

References
1
Resolving title…
app.any.run
MITRE ATT&CK
Rule Metadata
Rule ID
8d01b53f-456f-48ee-90f6-bc28e67d4e35
Status
test
Level
high
Type
Detection
Created
Mon Jul 11
Modified
Tue Feb 14
Author
Florian Roth (Nextron Systems)
Path
rules/windows/process_creation/proc_creation_win_powershell_base64_encoded_obfusc.yml
Raw Tags
attack.defense-evasion
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