1.背景

1.1 家族介绍

Medusa家族是一种主要针对基于Windows环境的勒索软件即服务（RaaS），自2021年6月起活跃。该勒索软件在2023年初因其活动升级而广为人知，特别是与其专用泄露网站Medusa Blog（DLS）的推出密切相关。Medusa的大多数攻击集中在美国，但也在英国、加拿大、澳大利亚等国家造成了重大影响，涉及众多行业。其高价值目标主要包括医疗保健、制造业、教育和专业服务等领域。

1.2 平台介绍

Medusa暗网地址搭建于Tor网络，结构可分为三个主要页面：数据泄露页、泄露详情页和谈判页。数据泄露页用于展示所有受害者的基本信息和已泄露的数据摘要，泄露详情页则深入展示具体的泄露内容、受影响的系统或企业细节，以增加受害者的压力。而谈判页则为受害者与Medusa黑客团队提供了匿名的聊天渠道，供双方进行赎金谈判，通常通过加密的消息传递方式确保信息安全。

2.恶意文件基础信息

2.1 加密器基本信息

2.2 勒索信

$$      $$ $$$$$$$$ $$$$$$$  $$   $$  $$$$$$   $$$$$$  
$$$    $$$ |$$  _____|$$  __$$ $$ |  $$ |$$  __$$ $$  __$$ 
$$$$  $$$$ |$$ |      $$ |  $$ |$$ |  $$ |$$ /  __|$$ /  $$ |
$$$$$$ $$ |$$$$$    $$ |  $$ |$$ |  $$ |$$$$$$  $$$$$$$$ |
$$ $$$  $$ |$$  __|   $$ |  $$ |$$ |  $$ | ____$$ $$  __$$ |
$$ |$  /$$ |$$ |      $$ |  $$ |$$ |  $$ |$$   $$ |$$ |  $$ |
$$ | _/ $$ |$$$$$$$$ $$$$$$$  |$$$$$$  |$$$$$$  |$$ |  $$ |
__|     __|________|_______/  ______/  ______/ __|  __|
-----------------------------[ Hello, PetroChina  !!! ]--------------------------

WHAT HAPPEND?
------------------------------------------------------------
1. We have PENETRATE your network and COPIED data.
* We have penetrated entire network including backup system and researched all about your data.
* And we have extracted all of your important and valuable data and copied them to private cloud storage.

2. We have ENCRYPTED your files.
While you are reading this message, it means all of your files and data has been ENCRYPTED by world's strongest ransomware.
All files have encrypted with new military-grade encryption algorithm and you can not decrypt your files.
But don't worry, we can decrypt your files.

There is only one possible way to get back your computers and servers - CONTACT us via LIVE CHAT and pay for the special 
MEDUSA DECRYPTOR and DECRYPTION KEYs.
This MEDUSA DECRYPTOR will restore your entire network, This will take less than 1 business day.


WHAT GUARANTEES?
---------------------------------------------------------------
We can post your data to the public and send emails to your customers.
We have professional OSINTs and media team for leak data to telegram, facebook, twitter channels and top news websites.

You can suffer significant problems due disastrous consequences, leading to loss of valuable intellectual property and other sensitive information, 
 costly incident response efforts, information misuse/abuse, loss of customer trust, brand and reputational damage, legal and regulatory issues.

    https://breached.vc/Forum-Leaks
    https://www.nulled.to/#!Leaks
    https://t.me/+yXOcSjVjI9tjM2E0

After paying for the data breach and decryption, we guarantee that your data will never be leaked and this is also for our reputation.

YOU should be AWARE!
---------------------------------------------------------------
We will speak only with an authorized person. It can be the CEO, top management, etc.
In case you ar not such a person - DON'T CONTACT US! Your decisions and action can result in serious harm to your company!
Inform your supervisors and stay calm!


If you do not contact us within 3 days, We will start publish your case to our official blog and everybody will start notice your incident!
--------------------[ Official blog tor address ]--------------------
Using TOR Browser(https://www.torproject.org/download/):

http://medus*******……uqsqyfry4ebnxlcbkccyd.onion/


CONTACT US!
----------------------[ Your company live chat address ]---------------------------
Using TOR Browser(https://www.torproject.org/download/):

http://medusaceg*******……sjcenhjena6uannk5f4xxxxxx.onion/6FpW****……

Or Use Tox Chat Program(https://qtox.github.io/)
Add user with our tox ID : 4AE***……

Our support email: ( [email protected] )

Company identification hash:

3.加密后文件分析

3.1 威胁分析

3.2 加密的测试文件

1. sierting.txt(852字节)

加密前

加密后

2. test1.bin(23,168,671字节)

加密前

文件的被加密数据以及未被加密数据的其中一部分

3. test2.bin(1,048,576字节)

加密前

文件的被加密数据以及未被加密数据的其中一部分

加密文件名特征

加密文件名 = 原始文件名 + .MEDUSA

加密文件数据特征

• 当文件的大小小于8kb时,全部加密
• 大于8kb且小于20mb时,加密头尾各4kb数据
• 大于20mb且小于92,160,000kb的时候,文件大小分成1,200kb每份,记录份数
• 根据份数分块,分块为(份数*4kb)大小每块,每块头部加密4kb,剩余部分不加密
• 组数大于76,800组(92,160,000kb)的时候,取76,800组
• 加密数据后,写入文件特征及加密后的aes密钥

加密文件结构

加密算法

文件加密使用了aes256加密算法的cbc模式，对加密文件的aes密钥采用了rsa加密,使用sha256生成受害者id。

密钥生成

aes256密钥为32字节随机数,使用库函数rand生成,种子为时间加上当前被加密文件的序号,iv为硬编码,加密aes256用的rsa公钥也为硬编码,受害者id根据rsa公钥进行sha256哈希。

iv: bytes([0x23,0x9F,0xF2,0xA9,0xDE,0x93,0x20,0x2F,0x24,0xBB,0xA5,0xFA,0xE0,0xA3,0x36,0xB1])

rsa公钥(pkcs1格式):

-----BEGIN RSA PUBLIC KEY-----
MIIBCgKCAQEAlEpVMPiNfBL/oZwlAI4J0Qx72kjd4IHuQxL65BALk1QyPNvR76HrG
ppGus9qcuu3aFP5DJyPDHnrWh4rwDTTmwmFPmMI9Ay7L3GdOmTdG9pWVRS6aNi1mR
PLnMmLn3hSH1PtyILR9H3SdoBTG3WtbnWNXynkmePr8baV6e6cpuq5wv8b25uaUn2
MJVotvrdRLxhw+e5Nj70GnePuy41hFbmA/LfOB1A6CPqJ8Neh0z6GNw6g6uMjkAHD
ED9btZ/9j4QgsFvQdpADHzG4aZSJW0JHRMIoTpvsIS/Q0Nbfr6qKXPXGBr6KAl9I8
eSRmtMkaauRvZ9yg+nicAVn1fVeBQIDAQAB
-----END RSA PUBLIC KEY-----

id: fb74336df24a22672b18f99406fde485af1aa79ad57fa3c92725bfc223f72538

4.逆向分析

4.1 大致行为描述

运行病毒后,程序读取命令行中的配置,根据配置自定义病毒行为,如加密根目录,是否隐藏主程序,勒索信路径等等.然后根据选项运行powershell命令,杀死对病毒不利的杀软进程和服务,删除卷影备份,以一定的规则(白名单)遍历文件夹并加密,然后在被加密文件的文件夹下写入勒索信.最后根据自定义配置决定是否延迟删除自身。

4.2 流程图

4.3 进入主函数

输出start字符串。

4.4 命令行解析

读取命令行参数,根据参数执行相应代码。

检测命令行是否为以下内容:

-V 输出版本
-d 自删除
-f 是否不包含系统目录
-i <path> 指定加密根目录
-k <path> 指定key文件路径
-n 感染网络驱动器
-p 执行"预处理"
-s 是否不包含系统驱动器
-t <path> 自定义勒索信路径
-v 隐藏黑窗口
-w <path> 设置powershell运行根目录

4.5 设置powershell执行策略

设置powershell执行策略,用于之后的命令执行,如延时自删除。

4.6 加载密钥相关

如果有文件,就从文件读取密钥

如果没有,则解密常量.其中获取bios信息的代码,经分析发现未被使用。

解密pkcs8格式rsa密钥,计算密钥的sha256,转为小写字符串作为用户id,再把该密钥转成pkcs1格式存储。

4.7 解密勒索信

如果勒索信文件存在,则读取。

不存在则解密默认勒索信。

4.8 预处理

解密白名单后缀和一些服务和进程名.根据配置内容确定加密根目录,以及是否执行所谓预处理。

执行所谓预处理,就是杀死对黑客不利的进程和删除卷影备份。

使用解密后的powershell命令，杀死如下进程和服务：

"Acronis VSS Provider","Enterprise Client Service","Sophos Agent","Sophos AutoUpdate Service","Sophos Clean Service","Sophos Device Control Service","Sophos File Scanner Service","Sophos Health Service","Sophos MCS Agent","Sophos MCS Client","Sophos Message Router","Sophos Safestore Service","Sophos System Protection Service","Sophos Web Control Service","SQLsafe Backup Service","SQLsafe Filter Service","Symantec System Recovery","Veeam Backup Catalog Data Service","AcronisAgent","AcrSch2Svc","Antivirus","ARSM","BackupExecAgentAccelerator","BackupExecAgentBrowser","BackupExecDeviceMediaService","BackupExecJobEngine","BackupExecManagementService","BackupExecRPCService","BackupExecVSSProvider","bedbg","DCAgent","EPSecurityService","EPUpdateService","EraserSvc11710","EsgShKernel","FA_Scheduler","IISAdmin","IMAP4Svc","macmnsvc","masvc","MBAMService","MBEndpointAgent","McAfeeEngineService","McAfeeFramework","McAfeeFrameworkMcAfeeFramework","McShield","McTaskManager","mfemms","mfevtp","MMS","mozyprobackup","MsDtsServer","MsDtsServer100","MsDtsServer110","MSExchangeES","MSExchangeIS","MSExchangeMGMT","MSExchangeMTA","MSExchangeSA","MSExchangeSRS","MSOLAP$SQL_2008","MSOLAP$SYSTEM_BGC","MSOLAP$TPS","MSOLAP$TPSAMA","MSSQL$BKUPEXEC","MSSQL$ECWDB2","MSSQL$PRACTICEMGT","MSSQL$PRACTTICEBGC","MSSQL$PROFXENGAGEMENT","MSSQL$SBSMONITORING","MSSQL$SHAREPOINT","MSSQL$SQL_2008","MSSQL$SYSTEM_BGC","MSSQL$TPS","MSSQL$TPSAMA","MSSQL$VEEAMSQL2008R2","MSSQL$VEEAMSQL2012","MSSQLFDLauncher","MSSQLFDLauncher$PROFXENGAGEMENT","MSSQLFDLauncher$SBSMONITORING","MSSQLFDLauncher$SHAREPOINT","MSSQLFDLauncher$SQL_2008","MSSQLFDLauncher$SYSTEM_BGC","MSSQLFDLauncher$TPS","MSSQLFDLauncher$TPSAMA","MSSQLSERVER","MSSQLServerADHelper100","MSSQLServerOLAPService","MySQL80","MySQL57","ntrtscan","OracleClientCache80","PDVFSService","POP3Svc","ReportServer","ReportServer$SQL_2008","ReportServer$SYSTEM_BGC","ReportServer$TPS","ReportServer$TPSAMA","RESvc","sacsvr","SamSs","SAVAdminService","SAVService","SDRSVC","SepMasterService","ShMonitor","Smcinst","SmcService","SMTPSvc","SNAC","SntpService","sophossps","SQLAgent$BKUPEXEC","SQLAgent$ECWDB2","SQLAgent$PRACTTICEBGC","SQLAgent$PRACTTICEMGT","SQLAgent$PROFXENGAGEMENT","SQLAgent$SBSMONITORING","SQLAgent$SHAREPOINT","SQLAgent$SQL_2008","SQLAgent$SYSTEM_BGC","SQLAgent$TPS","SQLAgent$TPSAMA","SQLAgent$VEEAMSQL2008R2","SQLAgent$VEEAMSQL2012","SQLBrowser","SQLSafeOLRService","SQLSERVERAGENT","SQLTELEMETRY","SQLTELEMETRY$ECWDB2","SQLWriter","SstpSvc","svcGenericHost","swi_filter","swi_service","swi_update_64","TmCCSF","tmlisten","TrueKey","TrueKeyScheduler","TrueKeyServiceHelper","UI0Detect","VeeamBackupSvc","VeeamBrokerSvc","VeeamCatalogSvc","VeeamCloudSvc","VeeamDeploymentService","VeeamDeploySvc","VeeamEnterpriseManagerSvc","VeeamMountSvc","VeeamNFSSvc","VeeamRESTSvc","VeeamTransportSvc","W3Svc","wbengine","WRSVC","MSSQL$VEEAMSQL2008R2","SQLAgent$VEEAMSQL2008R2","VeeamHvIntegrationSvc","swi_update","SQLAgent$CXDB","SQLAgent$CITRIX_METAFRAME","SQL Backups","MSSQL$PROD","Zoolz 2 Service","MSSQLServerADHelper","SQLAgent$PROD","msftesql$PROD","NetMsmqActivator","EhttpSrv","ekrn","ESHASRV","MSSQL$SOPHOS","SQLAgent$SOPHOS","AVP","klnagent","MSSQL$SQLEXPRESS","SQLAgent$SQLEXPRESS","wbengine","kavfsslp","KAVFSGT","KAVFS","mfefire","zoolz.exe","agntsvc.exe","dbeng50.exe","dbsnmp.exe","encsvc.exe","excel.exe","firefoxconfig.exe","infopath.exe","isqlplussvc.exe","msaccess.exe","msftesql.exe","mspub.exe","mydesktopqos.exe","mydesktopservice.exe","mysqld.exe","mysqld-nt.exe","mysqld-opt.exe","ocautoupds.exe","ocomm.exe","ocssd.exe","onenote.exe","oracle.exe","outlook.exe","powerpnt.exe","sqbcoreservice.exe","sqlagent.exe","sqlbrowser.exe","sqlservr.exe","sqlwriter.exe","steam.exe","synctime.exe","tbirdconfig.exe","thebat.exe","thebat64.exe","thunderbird.exe","visio.exe","winword.exe","wordpad.exe","xfssvccon.exe","tmlisten.exe","PccNTMon.exe","CNTAoSMgr.exe","Ntrtscan.exe","mbamtray.exe"

删除卷影备份。

4.9 遍历驱动器

遍历系统的驱动器列表,根据自定义的是否加密网络文件开关,选择性地忽略网络驱动器(DRIVE_REMOTE)。

4.10 加密文件

判断加密系统驱动器或加密系统目录选项是否开启。

是则加密指定目录下的文件.白名单路径和文件名如下:

"Windows","Windows.old","PerfLogs","MSOCache","Program Files","Program Files (x86)","ProgramData","\AppData\Local\Temp\","\AppData\LocalLow\","\AppData\Roaming\","\Users\All Users\"
"desktop.ini","Thumbs.db"

使用c++事务加密文件.入口点需要在汇编模式才能看到。

设置文件属性为非只读。

过滤一些白名单。

根据后缀判断是否加密过文件。

加密主要逻辑,使用了aes,aes使用windows自带api(cng)实现.使用硬编码的iv加密,加密结果写入文件.写入加密内容后,写入文件的尾部信息(格式上文有给出).最后在源文件名字符串后加上".MEDUSA"作为新文件名,使用MovFile替换源文件。

同时写入勒索信。

4.11 结束工作

计算并显示加密所用时间,再根据配置决定是否自删除。

使用powershell命令执行延时自删除。

5.病毒分析概览

主要的行为流程可以总结为：病毒启动后根据命令行配置定制行为，包括选择加密根目录、隐藏主程序、指定勒索信路径等，同时执行PowerShell命令结束反病毒进程、删除卷影备份，并通过命令行解析控制具体操作。病毒会设置PowerShell执行策略确保后续命令顺利执行，加载加密密钥并使用RSA算法加密存储密钥。如果勒索信文件存在，病毒读取并使用其中内容；若无，则解密默认勒索信。加密前，病毒会结束不利进程和删除备份，随后通过白名单规则遍历并加密文件，同时在每个加密文件所在的文件夹写入勒索信。文件加密的方式根据文件大小不同而有所区别。最后，根据配置，病毒可能延迟自删除以清除痕迹。

6.参考文章

https://www.attackiq.com/2024/09/19/emulating-medusa-ransomware/

https://thehackernews.com/2024/01/medusa-ransomware-on-rise-from-data.html

https://www.cisa.gov/news-events/cybersecurity-advisories/aa22-181a

https://www.vectra.ai/threat-actors/medusa

https://www.reliaquest.com/blog/medusa-attack-analysis/

教程分享篇聚焦于实际的安全防护方法，通过定期进行基线加固、及时更新补丁和备份数据等措施，为企业提供具体的操作指南，并在此基础上加强公司安全人员的意识培训，帮助企业有效防范勒索病毒的威胁。

如果您想了解有关勒索病毒的最新发展情况，或者需要获取相关帮助，请关注“solar专业应急响应团队”。