win_mewsei_auto

YARA detection rule by Felix Bilstein - yara-signator at cocacoding dot com

Detects win.mewsei.

rule win_mewsei_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2026-09-17"
        version = "1"
        description = "Detects win.mewsei."
        info = "autogenerated rule brought to you by yara-signator"
        tool = "yara-signator v0.6.0"
        signator_config = "callsandjumps;datarefs;binvalue"
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.mewsei"
        malpedia_rule_date = "20260916"
        malpedia_hash = "53a643781c18e08f4a50949af60172d837a0b6f6"
        malpedia_version = "20260917"
        malpedia_license = "CC BY-SA 4.0"
        malpedia_sharing = "TLP:WHITE"

    


    strings:
        $sequence_0 = { 57 8bf0 43 8d642400 53 e8???????? 8bf8 }
                                                                                                
        $sequence_1 = { 8bc8 8d86c39e2600 894508 c1e810 2bf9 25ff7f0000 33d2 }
                                                                                                
        $sequence_2 = { 337dfc 037de8 8dbc1f019546fd c1cf0a 037df8 0fb65822 }
                                                                                    
        $sequence_3 = { 8b5d08 56 57 8bf0 43 8d642400 }
                                                                                    
        $sequence_4 = { 83c404 57 894dfc e8???????? }
                                                            
        $sequence_5 = { 0bfb 0fb65818 c1e708 0bfb 8b5df8 897970 897dc8 }
                                                                                                
        $sequence_6 = { ebe6 56 8b35???????? 57 }
                                                            
        $sequence_7 = { c1cf0b 03fe f7d2 0bd7 }
                                                            
        $sequence_8 = { 83c410 6a06 53 ff15???????? }
                                                            
        $sequence_9 = { c1ea10 884708 8b4610 884f05 885706 8bc8 8bd0 }
                                                                                                
    condition:
        7 of them and filesize < 504832
}

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

bc3dd8f8-29ff-43cf-85b7-13fbaae0cf93

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

[[ reason ]]

What does this mean?

Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

[[ reason ]]

What do these messages mean?

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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