Mal_Backdoor_ChaChi_RAT
YARA-2025-1617
High
general
Active
ChaChi RAT used in PYSA Ransomware Campaigns
Mal_Backdoor_ChaChi_RAT.yar
Valid Syntax
rule Mal_Backdoor_ChaChi_RAT
{
meta:
description = "ChaChi RAT used in PYSA Ransomware Campaigns"
reference = "https://blogs.blackberry.com/en/2021/06/pysa-loves-chachi-a-new-golang-rat"
author = "BlackBerry Threat Research & Intelligence"
strings:
// "Go build ID:"
$go = { 47 6F 20 62 75 69 6C 64 20 49 44 3A }
// dnsStream
$dnsStream = { 64 6E 73 53 74 72 65 61 6D }
// SOCKS5
$socks5 = { 53 4F 43 4B 53 35 }
// chisel
$chisel = { 63 68 69 73 65 6C }
condition:
// MZ signature at offset 0
uint16(0) == 0x5A4D and
// PE signature at offset stored in MZ header at 0x3C
uint32(uint32(0x3C)) == 0x00004550 and
// ChaChi Strings
all of them
}
Rule Metadata
description
ChaChi RAT used in PYSA Ransomware Campaigns
reference
https://blogs.blackberry.com/en/2021/06/pysa-loves-chachi-a-new-golang-rat
author
BlackBerry Threat Research & Intelligence
String Definitions
{"name":"$go","value":"{ 47 6F 20 62 75 69 6C 64 20 49 44 3A }\n \/\/ dnsStream"}
{"name":"$dnsStream","value":"{ 64 6E 73 53 74 72 65 61 6D }\n \/\/ SOCKS5"}
{"name":"$socks5","value":"{ 53 4F 43 4B 53 35 }\n \/\/ chisel"}
{"name":"$chisel","value":"{ 63 68 69 73 65 6C }"}
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 Mal_Backdoor_ChaChi_RAT.yar /path/to/suspicious/file # Scan a directory recursively yara -r Mal_Backdoor_ChaChi_RAT.yar /path/to/directory/ # Scan with metadata output yara -m Mal_Backdoor_ChaChi_RAT.yar target_file # Scan process memory (Linux) yara Mal_Backdoor_ChaChi_RAT.yar /proc/[pid]/exe
Integration Examples
Python (yara-python)
import yara
rules = yara.compile(filepath='Mal_Backdoor_ChaChi_RAT.yar')
matches = rules.match('/path/to/file')
ClamAV Integration
clamscan --yara-rules=Mal_Backdoor_ChaChi_RAT.yar /path/to/scan
Rule Information
YARA ID
YARA-2025-1617
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
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