keydnap_backdoor_packer

YARA-2016-0206 High general Active

OSX/Keydnap packed backdoor

keydnap_backdoor_packer.yar Valid Syntax
// Keydnap packer yara rule
// https://github.com/eset/malware-ioc/
//
// These yara rules are provided to the community under the two-clause BSD
// license as follows:
//
// Copyright (c) 2016, ESET
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//


rule keydnap_backdoor_packer
{
    meta:
        description = "OSX/Keydnap packed backdoor"
        author = "Marc-Etienne M. Leveille"
        date = "2016-07-06"
        reference = "http://www.welivesecurity.com/2016/07/06/new-osxkeydnap-malware-is-hungry-for-credentials"
        version = "1"

    strings:
        $upx_string = "This file is packed with the UPX"
        $packer_magic = "ASS7"
        $upx_magic = "UPX!"
        
    condition:
        $upx_string and $packer_magic and not $upx_magic
}


Rule Metadata

description
OSX/Keydnap packed backdoor
author
Marc-Etienne M. Leveille
date
2016-07-06
reference
http://www.welivesecurity.com/2016/07/06/new-osxkeydnap-malware-is-hungry-for-credentials
version
1

String Definitions

{"name":"$upx_string","value":"\"This file is packed with the UPX\""}
{"name":"$packer_magic","value":"\"ASS7\""}
{"name":"$upx_magic","value":"\"UPX!\""}

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 keydnap_backdoor_packer.yar /path/to/suspicious/file

# Scan a directory recursively
yara -r keydnap_backdoor_packer.yar /path/to/directory/

# Scan with metadata output
yara -m keydnap_backdoor_packer.yar target_file

# Scan process memory (Linux)
yara keydnap_backdoor_packer.yar /proc/[pid]/exe

Integration Examples

Python (yara-python)

import yara
rules = yara.compile(filepath='keydnap_backdoor_packer.yar')
matches = rules.match('/path/to/file')

ClamAV Integration

clamscan --yara-rules=keydnap_backdoor_packer.yar /path/to/scan

Rule Information

YARA ID
YARA-2016-0206
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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