# Conti Ransomware

**blog.qualys.com/vulnerabilities-threat-research/2021/11/18/conti-ransomware**

Ghanshyam More November 18, 2021

Conti is a sophisticated Ransomware-as-a-Service (RaaS) model first detected in December 2019. Since its inception, its use has grown
rapidly and has even displaced the use of other RaaS tools like Ryuk. The Cybersecurity and Infrastructure Security Agency (CISA) and the
Federal Bureau of Investigation (FBI) issued a warning about Conti in Sept 2021, noting that they had observed it being used in more than 400
cyberattacks globally, though concentrated in North America and Europe.

The most common initial infection vectors used are spear phishing and RDP (Remote Desktop Protocol) services. Phishing emails work either
through malicious attachments, such as Word documents with an embedded macro that can be used to drop/download BazarLoader, Trickbot,
IceID trojans, or via social engineering tactics employed to get the victim to provide additional information or access credentials. Following
initial access, attackers download and execute a Cobalt Strike beacon DLL to gather information about domain admin accounts. Additionally,
threat actors use Kerberos attacks to attempt to get admin hash in order to conduct brute force attacks.

[A Conti affiliate recently leaked what has been dubbed the Conti playbook. The playbook revealed that Conti actors also exploit vulnerabilities](https://www.bleepingcomputer.com/news/security/translated-conti-ransomware-playbook-gives-insight-into-attacks/)
in unpatched assets to escalate privileges and move laterally across a victim’s network. They check for the “PrintNightmare” vulnerability
(CVE-2021-34527) in Windows Print spooler service, EternalBlue vulnerability (CVE-2017-0144) in Microsoft Windows Server Message Block,
and the “Zerologon” vulnerability (CVE-2020-1472) in Microsoft Active Directory Domain Controller. The playbook has been translated from
Russian to English by security researchers and has provided other useful Indicators of Compromise (IoC).

Conti actors also use the RouterScan tool to identify router devices in a provided range of IPs and attempt to find logins/passwords from a
standard list available with the RouterScan tool. They then install AnyDesk or Atera on the target machine to maintain an open communication
channel. Like other ransomware attacks, Conti actors exfiltrate data from victims’ networks to cloud storage services like MEGA and then
deploy Conti ransomware. To upload data on cloud storage Conti uses open-source Rclone command-line software. They use a double
extortion approach in which they demand a ransom to release the encrypted data or threaten to publicly release it if a ransom is not paid. They
may also sell the data to the highest bidder.

## Technical Details:

Conti ransomware uses obfuscation. The most notable use is to hide various Windows API calls used by the malware. It is common for some
malware to lookup API calls during execution. Initially, it brings import module names then decrypts the API names and gets their addresses.


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Fig. 1 De-obfuscation of Windows API
Conti uses a unique String Decryption Routine that is applied to almost every string text or API name used by the malware as shown in Fig. 2:

Fig.

2 String Decryption Routine
After getting API addresses, it calls for `CreateMutexA API with the Mutex Value of “CONTI” as shown below in Fig. 3:`

Fig. 3 Create

Mutex
It deletes Windows Volume Shadow Copies and also resizes shadow storage for drives C to H:


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Fig. 4 Deletes Windows Volume Shadow Copy
Next, Conti executes commands for stopping potential Windows Services related to antivirus, security, backup, database, and email solutions:

Fig. 5 Stop Potential Windows Services
The table below contains the names of the Windows Services that Conti stopped by calling the code in Fig. 5 in the loop.

MSSQL$BKUPEXEC MSSQL$SQLEXPRESS MSSQLFDLauncher$SHAREPOINT

MSSQL$ECWDB2 MSSQL$SYSTEM_BGC MSSQLFDLauncher$SQL_2008

MSSQL$PRACTICEMGT MSSQL$TPS MSSQLFDLauncher$SYSTEM_BGC

MSSQL$PRACTTICEBGC MSSQL$TPSAMA MSSQLFDLauncher$TPS

MSSQL$PROD MSSQL$VEEAMSQL2008R2 MSSQLFDLauncher$TPSAMA

MSSQL$PROFXENGAGEMENT MSSQL$VEEAMSQL2008R2 MSSQLSERVER

MSSQL$SBSMONITORING MSSQL$VEEAMSQL2012 MSSQLServerADHelper

MSSQL$SHAREPOINT MSSQLFDLauncher MSSQLServerADHelper100

MSSQL$SOPHOS MSSQLFDLauncher$PROFXENGAGEMENT MSSQLServerOLAPService

MSSQL$SQL_2008 MSSQLFDLauncher$SBSMONITORING MySQL57

Acronis VSS Provider Mfemms DCAgent

AcronisAgent Mfevtp EhttpSrv

AcrSch2Svc MMS Ekrn

Antivirus Mozyprobackup Enterprise Client Service

ARSM MsDtsServer EPSecurityService

AVP MsDtsServer100 EPUpdateService

BackupExecAgentAccelerator MsDtsServer110 EraserSvc11710

BackupExecAgentBrowser MSExchangeES EsgShKernel

BackupExecDeviceMediaService MSExchangeIS ESHASRV

BackupExecJobEngine MSExchangeMGMT FA_Scheduler

BackupExecManagementService MSExchangeMTA MSOLAP$TPSAMA

BackupExecRPCService MSExchangeSA McShield

BackupExecVSSProvider MSExchangeSRS McTaskManager

Bedbg msftesql$PROD Mfefire

IISAdmin MSOLAP$SQL_2008 Klnagent

IMAP4Svc MSOLAP$SYSTEM BGC MSOLAP$TPS


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Co t a so e e ages t e do s esta t a age to c ose app cat o s a d se ces t at a e u g o de to a e t e a a ab e o
encryption and to maximize the damage:

Fig. 6 Unlock files with Windows Restart Manager
It collects information about drives and drive types present on compromised systems:

Fig. 7 Collect Drives Information
As shown in Fig. 8, Conti uses multi-threaded tactics. It calls `CreateIoCompletionPort API to create multiple instances of worker threads`
into memory to wait for data. Once the file listing is completed, it is passed to the worker threads. Utilizing the computing power of multi-core
CPUs, the data is quickly encrypted:


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Fig. 8 Implementation of Multi-threaded Processing

Fig. 9 Multiple Threads Perform

File Encryption
Conti then iterates files on the local system and those on remote SMB network shares to determine what data to encrypt. It looks for folders
and drives shared on remote systems using `NetShareEnum API. If the remote share is accessible, it encrypts the files present in that share:`


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Fig. 10 Getting Info of Remote Shares
It collects ARP cache information from the local system using the `GetIpNetTable API. ARP cache information is a list of all the systems with`
which the computer recently communicated. It checks for “172.”, “192.168.” etc., on the collected IP list. If an IP address is in a different range
it skips that system from encryption:

Fig. 11 Collect ARP Cache Information
It uses an AES-256 encryption key per file with a hard-codedRAS-4096 public encryption key. As shown in Fig. 12, the 0x6610 parameter is
used while calling the `CryptGenKey API. 0x6610 is the value of the CALG_AES_256 identifier and is only alg_id:`

Fig. 12 Create CALG_AES_256 Key
Conti has a unique feature that allows attackers to perform file encryption in command line mode:


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Fig. 13 Command Line Mode of Operation

## Modes of Operation

Conti allows 2 command line modes `--encrypt-mode and` `- h :`

Fig. 14 Command Line `--encrypt-mode Mode`
```
--encrypt-mod marks which files are encrypted. There are 3 options for its value: all, local, and network . By default, ransomware

```
runs with the `all parameter:`

Fig.

15 Command Line `--encrypt-mode with Value` `all`
In `all, encryption carried out for – local and network.` `network means that shared resources on the local network will be encrypted:`

Fig. 16 Command Line `--encrypt-mode Mode with Value` `local`

Fig. 17 Command Line `--encrypt-mode Mode with Value` `network`
In command line `-h mode, the parameter may contain the name of a file that lists the DNS and NetBIOS addresses of remote servers. The`
malware will then build a list of folders to ignore during encryption:


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Fig. 18 Folders Ignored in Encryption
It skips the following extensions during encryption: .exe, .dll, .sys, .lnk, and .CONTI. It appends the file extension `.CONTI and creates a`
ransom note named `CONTI_README.txt in every folder to notify users about the infection:`

Fig. 19

__CONTI” Extension Appended to Files

## The Ransom Note:

The ransom note and the note’s file information are present in the resource of malware files:

Fig. 20 Ransom Note Content


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Fig. 21 Ransom Note Name
It calls the `LoadResource API to get ransom note-related information:`

Fig. 22 Code to Collect Data Related to the Ransom Note
The ransom note contains 2 email addresses to get in touch with the attackers. The addresses are unique for each victim:


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Fig. 23 Ransom Note

## IoC:
```
eae876886f19ba384f55778634a35a1d975414e83f22f6111e3e792f706301fe

 TTP Map:

```

**Credential**
**Access** **Discovery**


**Lateral**
**Movement** **Collect**


**Initial Access** **Execution** **Persistence**


**Privilege**
**Escalation** **Defense Evasion**


Valid
Accounts
(T1078)

Phishing:
Spearphishing
Attachment
(T1566.001)

Phishing:
Spearphishing
Link
(T1566.002)

Exploit publicfacing
application
(T1190)


Command and
Scripting
Interpreter:
Windows
Command
Shell
(T1059.003)

Native
Application
Programming
Interface (API)
(T1106)

Windows
Management
Instrumentation
(T1047)

User execution
(T1204)

Scheduled
task/job:
scheduled task
(T1053.005)

Command and
Scripting
Interpreter:
PowerShell
(T1059.001)


Valid
Accounts
(T1078)

External
Remote
Services
(T1133)

Scheduled
task/job:
scheduled
task
(T1053.005)

Startup item
(T1165)

Boot or
logon
autostart
execution:
Winlogon
Helper DLL
(T1547.004)


Process
Injection:
Dynamiclink Library
Injection
(T1055.001)

Valid
accounts:
domain
accounts
(T1078.002)


Obfuscated Files or
Information (T1027)

Process Injection:
Dynamic-link Library
Injection
(T1055.001)

Deobfuscate/Decode
Files or Information
(T1140)

Impair defenses:
disable or modify
tools (T1562.001)


Brute Force
(T1110)

Steal or
Forge
Kerberos
Tickets:
Kerberoasting
(T1558.003)

OS credential
dumping
(T1003)

Credentials
from
password
stores
(T1555)


System
Network
Configuration
Discovery
(T1016)

System
Network
Connections
Discovery
(T1049)

Process
Discovery
(T1057)

File and
Directory
Discovery
(T1083)

Network
Share
Discovery
(T1135)

Remote
System
Discovery
(T1018)

Network
Service
Scanning
(T1046)


Remote
Services:
SMB/Windows
Admin Shares
(T1021.002)

Taint Shared
Content
(T1080)

Exploitation of
Remote
Services
(T1210)

Lateral tool
transfer
(T1570)


Archive
Collecte
Data:
Archive
Utility
(T1560.


-----

**Credential**
**Access** **Discovery**

Permission
groups
discovery:
domain
groups
(T1069.002)

System
information
discovery
(T1082)

System
owner/user
discovery
(T1033)

Security
software
discovery
(T1063)

Account
Discovery:
Local
Account
(T1087.001)

Permissions
Group
Discovery:
Local Groups
(T1069.001)


**Lateral**
**Movement** **Collect**


**Initial Access** **Execution** **Persistence**

## Summary


**Privilege**
**Escalation** **Defense Evasion**


To defend against threats, Qualys recommends good cyber hygiene practices, and moving to a preventative approach by keeping network
configurations, backup, application access, and patching up-to-date.


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