YARA · SEKOIA.IO Community
SEKOIA_Koi_Netstealer
Detects NET ofbuscated Stealer used loaded by KoiLoader
- Author
- Sekoia.io
- Date
- 2024-03-20
- Modified
- 2024-12-19
- Score / Quality
- 75 / 80
What this rule detects
Detects NET ofbuscated Stealer used loaded by KoiLoader
Associated malware family: Koiloader.
Targets: Windows PE.
It defines 5 patterns (5 text, 0 hex, 0 regex).
Summary generated from the rule's metadata and condition.
Rule source
koi-netstealer.yarDetection Rule License 1.1
rule SEKOIA_Koi_Netstealer : FILE
{
meta:
= "Detects NET ofbuscated Stealer used loaded by KoiLoader"
= "Sekoia.io"
= "deb06e2a-848c-44b3-be95-017ebccf11f8"
= "2024-03-20"
= "2024-12-19"
= "https://github.com/SEKOIA-IO/Community"
= "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/koi_netstealer.yar#L1-L20"
= "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
= "814db1092820ff1ed9e592dc92c72ad73643eb6d68df9f593ed637434373e41b"
= 75
= 80
= "FILE"
= "1.0"
= "TLP:CLEAR"
strings:
$name_1 = "pg20"
$name_2 = "pg40"
$s1 = "Curve25519"
$s2 = "ConsoleApp"
$s3 = "e0d2eec7-eb14-48ba-8709-dcc9de65947d"
condition:
uint16be( 0 ) == 0x4d5a and filesize < 150KB and any of ( $name_* ) and all of ( $s* )
}
Strings (5 patterns)
| Identifier | Type | Value | Modifiers |
|---|---|---|---|
| $name_1 | text | "pg20" | |
| $name_2 | text | "pg40" | |
| $s1 | text | "Curve25519" | |
| $s2 | text | "ConsoleApp" | |
| $s3 | text | "e0d2eec7-eb14-48ba-8709-dcc9de65947d" |
Condition
uint16be( 0 ) == 0x4d5a and filesize < 150KB and any of ( $name_* ) and all of ( $s* )In plain words (Heuristic)
- The file must start with “MZ” — a Windows executable (PE).
- The file must be smaller than 150KB (a cheap guard that skips large files).
- All patterns in ( $s* ) must match.
- At least one pattern in ( $name_* ) 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.
Drop a file here or click to chooseScanned locally with YARA-X. Files up to 200 MB.
References
Licence & attribution
Author: Sekoia.io
Source repository: SEKOIA.IO Community @ a438a5901a
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: deb06e2a-848c-44b3-be95-017ebccf11f8
Metadata
| version | 1.0 |
|---|---|
| classification | TLP:CLEAR |
Tags:FILE
Related rules
- MalwareSEKOIA.IO Community· Sekoia.io· 2024-03-20
- MalwareSEKOIA.IO Community· Sekoia.io· 2024-03-20
- MalwareSEKOIA.IO Community· Sekoia.io· 2024-03-20
- MalwareMalpedia signator rules· Felix Bilstein - yara-signator at cocacoding dot com· 2026-05-04
- MalwareCAPE Sandbox (CAPEv2)· YungBinary· 2024-10-25
- RUSSIANPANDA_Win_Mal_Koi_LoaderMetadata onlyMalwareRussianPanda· RussianPanda· 2024-04-04
- RUSSIANPANDA_Win_Mal_Koi_Loader_DecryptedMetadata onlyMalwareRussianPanda· RussianPanda· 2024-04-04
- MalwareSEKOIA.IO Community· Sekoia.io· 2024-07-16