win_asyncrat_bytecodes

YARA detection rule by Matthew @ Embee_Research

Detects bytecodes present in unobfuscated AsyncRat Samples. Rule may also pick up on other Asyncrat-derived malware (Dcrat/venom etc)

import "dotnet"
rule win_asyncrat_bytecodes
{
	meta:
		author = "Matthew @ Embee_Research"
		created = "2023/09/10"
		description = "Detects bytecodes present in unobfuscated AsyncRat Samples. Rule may also pick up on other Asyncrat-derived malware (Dcrat/venom etc)"
		sha_256 = "0e65aadd6c3aede82c01e66723fd3688ffa3a0ab6600c8556b393c5f2615a15d"
		
	strings:
	
		$s1 = {72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 72 ?? ?? ?? ?? 80 ?? ?? ?? ?? 2A}
		
	condition:
			dotnet.is_dotnet 
		and
			filesize < 7000KB 
		and 
			$s1
}

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

74e9fe5e-1779-4e5d-a409-e6e62ca0dae2

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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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