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Adding lzma executor and diverse python indicators #1839

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merged 2 commits into from
Nov 21, 2024
Merged

Adding lzma executor and diverse python indicators #1839

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52cb8f7
Adding lzma executor and diverse python indicators
gdesmar Nov 18, 2024
9b27d79
Switching from mandatory base64 to one-of base64,zlib,lzma
gdesmar Nov 18, 2024
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14 changes: 12 additions & 2 deletions assemblyline/common/custom.yara
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Original file line number Diff line number Diff line change
Expand Up @@ -792,6 +792,12 @@ rule code_python {

$strong_py20 = "asyncio.run("
$strong_py21 = "asyncio.sleep("
$strong_py22 = "pty.spawn("
$strong_py23 = "platform.system()"
$strong_py24 = "subprocess.run("
$strong_py25 = "subprocess.Popen("
$strong_py26 = "base64.b64decode("
$strong_py27 = "socket.socket("

// Setup.py indicators
$strong_py50 = "python_requires" ascii wide
Expand Down Expand Up @@ -828,16 +834,20 @@ rule code_python {
$strong_py152 = "os.rename("


// High confidence one-liner used to execute base64 blobs
// High confidence one-liner used to execute encoded blobs
// reference: https://github.com/DataDog/guarddog/blob/main/guarddog/analyzer/sourcecode/exec-base64.yml
$executor1 = /((exec|eval|check_output|run|call|[Pp]open|os\.system)\(|lambda[ \t]+\w{1,100}[ \t]*:[ \t]*)((zlib|__import__\((['"]zlib['"]|['"]\\x0*7a\\x0*6c\\x0*69\\x0*62['"]|['"]\\0*172\\0*154\\0*151\\0*142['"])\))\.decompress\()?(base64|__import__\((['"]base64['"]|['"]\\x0*62\\x0*61\\x0*73\\x0*65\\x0*36\\x0*34['"]|['"]\\0*142\\0*141\\0*163\\0*145\\0*66\\0*64['"])\))\.b64decode\(/
$executor1 = /((exec|eval|check_output|run|call|[Pp]open|os\.system)\(|lambda[ \t]+\w{1,100}[ \t]*:)\s*(((zlib|__import__\((['"]zlib['"]|['"]\\x0*7a\\x0*6c\\x0*69\\x0*62['"]|['"]\\0*172\\0*154\\0*151\\0*142['"])\)|lzma|__import__\((['"]lzma['"]|['"]\\x0*6c\\x0*7a\\x0*6d\\x0*61['"]|['"]\\0*154\\0*172\\0*155\\0*141['"])\))\.decompress\()|(base64|__import__\((['"]base64['"]|['"]\\x0*62\\x0*61\\x0*73\\x0*65\\x0*36\\x0*34['"]|['"]\\0*142\\0*141\\0*163\\0*145\\0*66\\0*64['"])\))\.b64decode\()/
$executor2 = /(marshal|__import__\((['"]marshal['"]|['"]\\x0*6d\\x0*61\\x0*72\\x0*73\\x0*68\\x0*61\\x0*6c['"]|['"]\\0*155\\0*141\\0*162\\0*163\\0*150\\0*141\\0*154['"])\)|pickle|__import__\((['"]pickle['"]|['"]\\x0*70\\x0*69\\x0*63\\x0*6b\\x0*6c\\x0*65['"]|['"]\\0*160\\0*151\\0*143\\0*153\\0*154\\0*145['"])\))\.loads\(/

condition:
mime startswith "text"
and (
2 of ($strong_py*)
or any of ($executor*)
or (
filesize < 1024
and 1 of ($strong_py*)
)
)
}

Expand Down