StormDNS

YARA detection rule by @bartblaze · MIT

Identifies StormDNS, a DNS shell used by Storm-260 to receive and execute commands from a C2.

rule StormDNS
{
    meta:
        id = "75nX2TPCk53RAhU55yBeFd"
        fingerprint = "v1_sha256_542a8af37bd4bc18218190cd82495146a4daa5d01db24804b9ff16ff04023a5a"
        version = "1.0"
        date = "2025-07-24"
        modified = "2025-07-24"
        status = "RELEASED"
        sharing = "TLP:CLEAR"
        source = "BARTBLAZE"
        author = "@bartblaze"
        description = "Identifies StormDNS, a DNS shell used by Storm-260 to receive and execute commands from a C2."
        category = "MALWARE"
        malware = "STORMDNS"
        malware_type = "WEBSHELL"
        reference = "https://www.microsoft.com/en-us/security/blog/2025/07/22/disrupting-active-exploitation-of-on-premises-sharepoint-vulnerabilities"
        hash = "1eb914c09c873f0a7bcf81475ab0f6bdfaccc6b63bf7e5f2dbf19295106af192"

    strings:
        $str_a = "Slept for %d seconds"
        $str_b = "Failed to allocate memory"
        $str_c = "cmd.exe /c %s 2>&1"
        $str_d = "Failed to execute command"
        $str_e = "Failed to reallocate memory"
        $str_f = "Command executed with no output"
        $str_g = "fragment_received"
        $str_h = "result_received"
        $str_i = "s%st%04zup%04zu"
        
        $pdb_part = "\\work\\tools\\ak47c2\\"
        $pdb_full = "C:\\Users\\Administrator\\Desktop\\work\\tools\\ak47c2\\dnsclinet-c\\dnsclient\\x64\\Release\\dnsclient.pdb"

    condition:
        8 of ($str_*) or any of ($pdb_*)
}

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

8b6eed9c-fe54-4366-987b-afc54dad31a8

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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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