Backdoor_Win_C3_1
YARA-2025-1955
High
general
Active
Detection to identify the Custom Command and Control (C3) binaries.
Backdoor_Win_C3_1.yar
Valid Syntax
rule Backdoor_Win_C3_1
{
meta:
author = "FireEye"
date_created = "2021-05-11"
description = "Detection to identify the Custom Command and Control (C3) binaries."
reference = "https://www.mandiant.com/resources/shining-a-light-on-darkside-ransomware-operations"
md5 = "7cdac4b82a7573ae825e5edb48f80be5"
strings:
$dropboxAPI = "Dropbox-API-Arg"
$knownDLLs1 = "WINHTTP.dll" fullword
$knownDLLs2 = "SHLWAPI.dll" fullword
$knownDLLs3 = "NETAPI32.dll" fullword
$knownDLLs4 = "ODBC32.dll" fullword
$tokenString1 = { 5B 78 5D 20 65 72 72 6F 72 20 73 65 74 74 69 6E 67 20 74 6F 6B 65 6E }
$tokenString2 = { 5B 78 5D 20 65 72 72 6F 72 20 63 72 65 61 74 69 6E 67 20 54 6F 6B 65 6E }
$tokenString3 = { 5B 78 5D 20 65 72 72 6F 72 20 64 75 70 6C 69 63 61 74 69 6E 67 20 74 6F 6B 65 6E }
condition:
filesize < 5MB and uint16(0) == 0x5A4D and uint32(uint32(0x3C)) == 0x00004550 and (((all of ($knownDLLs*)) and ($dropboxAPI or (1 of ($tokenString*)))) or (all of ($tokenString*)))
}
Rule Metadata
author
FireEye
date_created
2021-05-11
description
Detection to identify the Custom Command and Control (C3) binaries.
reference
https://www.mandiant.com/resources/shining-a-light-on-darkside-ransomware-operations
md5
7cdac4b82a7573ae825e5edb48f80be5
String Definitions
{"name":"$dropboxAPI","value":"\"Dropbox-API-Arg\""}
{"name":"$knownDLLs1","value":"\"WINHTTP.dll\" fullword"}
{"name":"$knownDLLs2","value":"\"SHLWAPI.dll\" fullword"}
{"name":"$knownDLLs3","value":"\"NETAPI32.dll\" fullword"}
{"name":"$knownDLLs4","value":"\"ODBC32.dll\" fullword"}
{"name":"$tokenString1","value":"{ 5B 78 5D 20 65 72 72 6F 72 20 73 65 74 74 69 6E 67 20 74 6F 6B 65 6E }"}
{"name":"$tokenString2","value":"{ 5B 78 5D 20 65 72 72 6F 72 20 63 72 65 61 74 69 6E 67 20 54 6F 6B 65 6E }"}
{"name":"$tokenString3","value":"{ 5B 78 5D 20 65 72 72 6F 72 20 64 75 70 6C 69 63 61 74 69 6E 67 20 74 6F 6B 65 6E }"}
Threat Analysis
This YARA rule is designed to detect general threats.
Severity Level: High
The rule uses pattern matching to identify specific byte sequences, strings, or behavioral patterns associated with malicious activity.
Detection Capabilities
- File-based detection for executables and documents
- Memory scanning for running processes
- Network traffic analysis support
Command Line Usage
# Scan a single file yara Backdoor_Win_C3_1.yar /path/to/suspicious/file # Scan a directory recursively yara -r Backdoor_Win_C3_1.yar /path/to/directory/ # Scan with metadata output yara -m Backdoor_Win_C3_1.yar target_file # Scan process memory (Linux) yara Backdoor_Win_C3_1.yar /proc/[pid]/exe
Integration Examples
Python (yara-python)
import yara
rules = yara.compile(filepath='Backdoor_Win_C3_1.yar')
matches = rules.match('/path/to/file')
ClamAV Integration
clamscan --yara-rules=Backdoor_Win_C3_1.yar /path/to/scan
Rule Information
YARA ID
YARA-2025-1955
Author
Repository
Created
August 19, 2025
Last Updated
August 19, 2025
Last Imported
Never
Threat Intelligence
Risk Level
High
Category
general
Detection Confidence
Analysis Pending
False Positive Rate
Not Available
Last Seen in Wild
No Data
Related Rules
Export Options
Similar Rules in general
YARA-2023-0001
CRI
Detect_Mimic_Ransomware
Detect_Mimic_Ransomware
YARA-2023-0002
MED
SystemBC_malware
Detect_SystemBC
YARA-2023-0003
MED
detect_catB
detect_CatB_ransomware
YARA-2022-0001
MED
detect_Typhon_Stealer
detect_Typhon_Stealer
YARA-2023-0004
MED
Nosu_stealer
Detect_Nosu_stealer
YARA-2022-0002
MED
detect_Lumma_stealer
detect_Lumma_stealer
YARA-2022-0003
MED
detect_StrelaStealer
detect_StrelaStealer
YARA-2022-0004
MED
detect_silence_Downloader
detect_silence_Downloader