YARA · Signature Base (Florian Roth / Nextron)
SIGNATURE_BASE_SUSP_JS_Dropper_Mar26
Detects suspicious JavaScript dropper used in plain-crypto-js supply chain attacks
- Author
- Marius Benthin
- Date
- 2026-03-31
- Modified
- 2026-05-15
- Score / Quality
- 70 / 85
What this rule detects
Detects suspicious JavaScript dropper used in plain-crypto-js supply chain attacks
It defines 7 patterns (7 text, 0 hex, 0 regex).
Summary generated from the rule's metadata and condition.
Rule source
rule SIGNATURE_BASE_SUSP_JS_Dropper_Mar26 : FILE
{
meta:
= "Detects suspicious JavaScript dropper used in plain-crypto-js supply chain attacks"
= "Marius Benthin"
= "456a52c2-9cbf-572f-9a5b-b8d74183e3f4"
= "2026-03-31"
= "2026-05-15"
= "https://www.stepsecurity.io/blog/axios-compromised-on-npm-malicious-versions-drop-remote-access-trojan"
= "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/mal_npm_supply_chain_mar26.yar#L19-L41"
= "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
= "e10b1fa84f1d6481625f741b69892780140d4e0e7769e7491e5f4d894c2e0e09"
= "9dad4bef8cf31a91240dbbc438eff2640389424db9f75be2d897d745133785ee"
= 70
= 85
= "FILE"
strings:
$sa1 = "Buffer.from("
$sa2 = "FileSync("
$sa3 = ".replaceAll("
$sb1 = ".arch()"
$sb2 = ".platform()"
$sb3 = ".release()"
$sb4 = ".type()"
condition:
filesize < 10KB and all of ( $sa* ) and 2 of ( $sb* )
}
Strings (7 patterns)
| Identifier | Type | Value | Modifiers |
|---|---|---|---|
| $sa1 | text | "Buffer.from(" | |
| $sa2 | text | "FileSync(" | |
| $sa3 | text | ".replaceAll(" | |
| $sb1 | text | ".arch()" | |
| $sb2 | text | ".platform()" | |
| $sb3 | text | ".release()" | |
| $sb4 | text | ".type()" |
Condition
filesize < 10KB and all of ( $sa* ) and 2 of ( $sb* )In plain words (Heuristic)
- The file must be smaller than 10KB (a cheap guard that skips large files).
- All patterns in ( $sa* ) must match.
- At least 2 patterns in ( $sb* ) must match.
Test this rule in your browser
Drop a file to scan it with this rule using YARA-X compiled to WebAssembly. Nothing is uploaded.
Sample hashes
Hashes of samples the author lists in the rule's meta (look them up in your threat-intelligence platform).
- e10b1fa84f1d6481625f741b69892780140d4e0e7769e7491e5f4d894c2e0e09
Licence & attribution
Author: Marius Benthin
Source repository: Signature Base (Florian Roth / Nextron) @ 94a1c48d7a
Licence: Detection Rule License 1.1 (repository licence)
Mirrored via YARA Forge 20260927, which prefixes rule names with the source and adds normalised meta fields.
Rule id: 456a52c2-9cbf-572f-9a5b-b8d74183e3f4
Tags:FILE
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