fileless_attack_via_regsvr32exe

rule fileless_attack_via_regsvr32exe {
 meta:
    author = "Ariel Millahuel"
    description = "Detects suspicious behavior in the utilization of regsvr32.exe and also a possible fileless attack via this executable.  License: https://github.com/Neo23x0/sigma/blob/master/LICENSE.Detection.Rules.md."
    reference = "https://tdm.socprime.com/tdm/info/KO6EuyFYoCN8"
    version = "0.01"
    created = "2019/11/26"
    category = "process_creation"
    product = "windows"
    mitre = "execution, defense evasion, t1218, t1218.010, t1059, t1059.003"

  events:
(re.regex($selection.target.process.command_line, `.*regsvr32.*`) and ($selection.metadata.product_event_type = "4688" or $selection.metadata.product_event_type = "1") and re.regex($selection.target.process.command_line, `.*/s.*`) and re.regex($selection.target.process.command_line, `.*/i.*`) and (re.regex($selection.target.process.command_line, `.*\.txt.*`) or re.regex($selection.target.process.command_line, `.*\.dll.*`)))

  condition:
    $selection
}