powershell_obfuscation_by_agenttesla

Description

AgentTesla downloads malware by using obfuscated powershell via ftp server on French Data Center License: https://github.com/Neo23x0/sigma/blob/master/LICENSE.Detection.Rules.md.

Query · yara_l

events:
((re.regex($selection1.target.process.file.full_path, `.*\\powershell`) and (re.regex($selection1.target.process.command_line, `Powershell $VN=\( '104{100e121'\.SpLiT\('!X_AeZuG{%'\) |fOreACh-oBjeCt{[CHar]\($_-BXOR 0x21 \) }\) -joIN '';sal MUM $VN;$BCmiLrM=@\(.*`) or re.regex($selection1.target.process.command_line, `Powershell '\(&'\+'\(G'\+'C'\+'###'\.replace\('###','M'\)\+' .*W-'\+'O.*\)'\+ 'Ne'\+'t\.'\+'W'\+'eb'\+'C'\+'li'\+'ent\)'\+'\.D'\+'ow'\+'nl'\+'oad'\+'F'\+'il'\+'e\(''.*File\.vbs.*`))) or (re.regex($selection1.target.process.file.full_path, `.*\\RegAsm\.exe`) and re.regex($selection1.principal.process.file.full_path, `.*\\InstallUtil\.exe`)))

  condition:
    $selection1
}
Raw source powershell_obfuscation_by_agenttesla · YARA-L
Esc
Published by chronicle/detection-rules ↗, licensed under Apache 2.0 ↗. Reproduced here unmodified. 
rule powershell_obfuscation_by_agenttesla {
 meta:
    author = "Emir Erdogan"
    description = "AgentTesla downloads malware by using obfuscated powershell via ftp server on French Data Center  License: https://github.com/Neo23x0/sigma/blob/master/LICENSE.Detection.Rules.md."
    reference = "https://tdm.socprime.com/tdm/info/lZkiLjSHfmwQ"
    version = "0.01"
    created = "2021-03-09"
    product = "windows"
    service = "sysmon"
    mitre = "T1064, T1060, T1081, T1130"

  events:
((re.regex($selection1.target.process.file.full_path, `.*\\powershell`) and (re.regex($selection1.target.process.command_line, `Powershell $VN=\( '104{100e121'\.SpLiT\('!X_AeZuG{%'\) |fOreACh-oBjeCt{[CHar]\($_-BXOR 0x21 \) }\) -joIN '';sal MUM $VN;$BCmiLrM=@\(.*`) or re.regex($selection1.target.process.command_line, `Powershell '\(&'\+'\(G'\+'C'\+'###'\.replace\('###','M'\)\+' .*W-'\+'O.*\)'\+ 'Ne'\+'t\.'\+'W'\+'eb'\+'C'\+'li'\+'ent\)'\+'\.D'\+'ow'\+'nl'\+'oad'\+'F'\+'il'\+'e\(''.*File\.vbs.*`))) or (re.regex($selection1.target.process.file.full_path, `.*\\RegAsm\.exe`) and re.regex($selection1.principal.process.file.full_path, `.*\\InstallUtil\.exe`)))

  condition:
    $selection1
}

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