YARA · Embee Research
EMBEERESEARCH_Win_Quasar_Rat_Client
Detects strings present in Quasar Rat Samples.
- Author
- Matthew @ Embee_Research
- Date
- 2023-08-27
- Modified
- 2023-10-18
- Score / Quality
- 75 / 75
What this rule detects
Detects strings present in Quasar Rat Samples.
Targets: Windows PE, .NET assembly.
It defines 5 patterns (5 text, 0 hex, 0 regex). YARA modules used: dotnet.
YARA-X says: warning[deprecated_field]: field `number_of_resources` is deprecated
Summary generated from the rule's metadata and condition.
Rule source
Includes the imports needed to compile it on its own.
import "dotnet"
rule EMBEERESEARCH_Win_Quasar_Rat_Client : FILE
{
meta:
= "Detects strings present in Quasar Rat Samples."
= "Matthew @ Embee_Research"
= "7fc0bd6d-e187-51b7-a8b8-68b17271cef8"
= "2023-08-27"
= "2023-10-18"
= "https://github.com/embee-research/Yara-detection-rules/"
= "https://github.com/embee-research/Yara-detection-rules//blob/ac56d6f6fd2a30c8cb6e5c0455d6519210a8b0f4/Rules/win_quasar_rat_client_aug_2023.yar#L3-L37"
= "N/A"
= "914d88f295ac2213f37d3f71e6d4383979283d1728079a208f286effb44d840c"
= "45a724179ae1d08044c4bafb69c7f9cdb4ed35891dc9cf24aa664d75464ceb6d"
= "7e13bcd73232c3f33410aa95f61e1196a2f9ae35e05c1f9c8f251e07077a9dfb"
= "efba911780ffb144f277e88ff8ca8f53a90c32a677ccb19ec26e71f974a1b91f"
= 75
= 75
= "FILE"
strings:
$s1 = "Quasar Client" ascii wide
$s2 = "Quasar.Client.Properties.Resources" ascii wide
$s3 = "Google\\Chrome\\User Data\\Default\\" wide
$s4 = "\\Mozilla\\Firefox\\Profiles" wide
$s5 = "Yandex\\YandexBrowser\\User Data\\Default\\" wide
condition:
uint16( 0 ) == 0x5a4d and dotnet.is_dotnet and filesize < 7000KB and ( for any i in ( 0 .. dotnet.number_of_resources -1 ) : ( dotnet.resources [ i ] . name == "Quasar.Client*" ) or ( 3 of ( $s* ) ) )
}
Strings (5 patterns)
| Identifier | Type | Value | Modifiers |
|---|---|---|---|
| $s1 | text | "Quasar Client" | ascii wide |
| $s2 | text | "Quasar.Client.Properties.Resources" | ascii wide |
| $s3 | text | "Google\\Chrome\\User Data\\Default\\" | wide |
| $s4 | text | "\\Mozilla\\Firefox\\Profiles" | wide |
| $s5 | text | "Yandex\\YandexBrowser\\User Data\\Default\\" | wide |
Condition
uint16( 0 ) == 0x5a4d and dotnet.is_dotnet and filesize < 7000KB and ( for any i in ( 0 .. dotnet.number_of_resources -1 ) : ( dotnet.resources [ i ] . name == "Quasar.Client*" ) or ( 3 of ( $s* ) ) )In plain words (Heuristic)
- The file must start with “MZ” — a Windows executable (PE).
- The file must be smaller than 7000KB (a cheap guard that skips large files).
- At least 3 patterns in ( $s* ) must match.
- A for-loop checks a property over several matches or items.
- Uses the dotnet module.
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).
- 914d88f295ac2213f37d3f71e6d4383979283d1728079a208f286effb44d840c
- 45a724179ae1d08044c4bafb69c7f9cdb4ed35891dc9cf24aa664d75464ceb6d
- 7e13bcd73232c3f33410aa95f61e1196a2f9ae35e05c1f9c8f251e07077a9dfb
Licence & attribution
Author: Matthew @ Embee_Research
Source repository: Embee Research @ ac56d6f6fd
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: 7fc0bd6d-e187-51b7-a8b8-68b17271cef8
Tags:FILE
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