HardBit 4.0: The Silent Network Ransomware

Introduction

Ransomware attacks continue to be one of the most dangerous cyber threats facing organizations worldwide. Among the newer and more stealthy threats is HardBit 4.0 ransomware, an upgraded version of a malware family that has been active since 2022.

HardBit 4.0 represents a significant evolution in ransomware design. Instead of relying on flashy data leaks or public shaming tactics, this ransomware focuses on quiet persistence, strong encryption, and advanced evasion techniques. Its ability to remain hidden while maintaining long-term access makes it especially dangerous for businesses and enterprises.

What Is HardBit 4.0?

HardBit 4.0 is a file-encrypting ransomware operated by cybercriminals who primarily target poorly secured network services. Unlike many modern ransomware groups, HardBit actors do not operate a public leak site and do not focus on double extortion tactics. Their strategy is simple but effective:
encrypt critical systems and demand ransom for decryption.

This focused approach allows attackers to move quietly, often remaining undetected until the encryption phase begins.

How the HardBit 4.0 Attack Starts

1. Initial Access – Exploiting Open RDP and SMB

The attack usually begins with brute-force attacks against exposed network services, particularly:

Remote Desktop Protocol (RDP)
Server Message Block (SMB)

Organizations that leave these services open to the internet without strong passwords or multi-factor authentication become easy targets. Once valid credentials are found, attackers gain direct access to internal systems.

2. Credential Harvesting and Lateral Movement

After entering the network, HardBit operators immediately attempt to harvest additional credentials. This allows them to:

Move laterally across the network
Access higher-privileged accounts
Identify valuable systems such as file servers and backups

This phase significantly increases the damage potential of the attack.

Multi-Stage Malware Deployment Using Neshta

One of the most unique aspects of HardBit 4.0 is its use of Neshta, a file-infecting virus that has existed since 2003.

Why Neshta Matters

Neshta infects executable files, making detection extremely difficult.
It acts as a dropper, secretly delivering the HardBit 4.0 ransomware.
Traditional antivirus tools often fail to detect it due to its file-infecting nature.

Neshta’s Execution Process

The dropper follows a four-stage deployment process:

Reads its own binary file and extracts the HardBit payload from memory.
Decrypts the ransomware code.
Writes the reconstructed ransomware to the system’s temporary directory.
Executes the ransomware using legitimate Windows system functions.

Persistence Mechanisms

HardBit 4.0 ensures it survives system reboots by:

Copying itself to the system root directory as a hidden file
Modifying Windows Registry keys so that every executable launched triggers the malware first

This level of persistence allows attackers to maintain long-term access even after partial cleanup attempts.

Defense Evasion Techniques

HardBit 4.0 aggressively disables security defenses to remain undetected.

Security Features Targeted

The malware modifies Windows Registry entries to disable:

Windows Defender Real-Time Monitoring
Tamper Protection
Anti-Spyware protections

Additionally, the ransomware binary is heavily obfuscated using a modified version of ConfuserEx, making reverse engineering extremely difficult for analysts.

Passphrase Protection – A Unique Feature

A standout feature of HardBit 4.0 is its runtime passphrase requirement.
The ransomware will only fully execute if the correct authorization key is supplied by the attackers.

Why This Is Important

Prevents accidental execution in sandbox environments
Makes automated malware analysis harder
Reduces the chances of early detection by security researchers

Encryption and Ransom Phase

Once the attackers are confident they control the network:

Files are encrypted across critical systems
Backups and shadow copies may be deleted
Victims receive a ransom note demanding payment for decryption

Unlike many ransomware families, HardBit relies entirely on encryption pressure, not public data leaks.

Indicators of Compromise (IOCs)

Organizations should watch for the following warning signs:

Network & Access Indicators

Repeated failed RDP or SMB login attempts
Sudden successful logins from unfamiliar IP addresses
Unusual lateral movement activity

File & System Indicators

Presence of Neshta-infected executables
Hidden files in system root directories
Unexpected files in %TEMP% directories

Registry Indicators

Modifications to: HKLM\SOFTWARE\Classes\exefile\shell\open\command

Disabled Windows Defender and Anti-Spyware settings

Behavioral Indicators

Security services unexpectedly stopped
Credential dumping activity (e.g., Mimikatz artifacts)
Unusual system slowdowns prior to encryption

Threat Actor Profile

HardBit 4.0 is attributed to organized cybercriminal ransomware operators rather than nation-state actors.
Their tactics indicate:

High technical skill
Strong focus on stealth and persistence
Long-term access over quick exposure

How Organizations Can Defend Against HardBit 4.0

Recommended Security Measures

Close or restrict public RDP and SMB access
Enforce strong passwords and multi-factor authentication
Monitor logs for brute-force attempts
Maintain offline and isolated backups
Use endpoint detection and response (EDR) solutions
Regularly audit registry changes and startup behavior

MITRE ATT&CK Mapping for HardBit 4.0

SIEM Detection Use Cases & Queries

1. RDP Brute-Force Detection

Log Source

Windows Security Logs
Firewall Logs

SIEM Logic

Detect multiple failed logins followed by a successful one.

Splunk Query

index=wineventlog EventCode=4625
| stats count by Account_Name, Source_Network_Address
| where count > 10

Follow-up successful login:

index=wineventlog EventCode=4624
| search Logon_Type=10

2. SMB Brute-Force or Abuse Detection

Splunk Query

index=wineventlog EventCode=4625
| search Logon_Type=3
| stats count by Source_Network_Address
| where count > 15

3. Credential Dumping (Mimikatz Behavior)

XDR / EDR Telemetry

Process creation logs
Memory access alerts

Splunk

index=sysmon EventCode=10
| search TargetImage="lsass.exe"

High Confidence Alert
Any non-system process accessing lsass.exe.

4. Neshta File Infection Detection

Behavior-Based Detection

Executables launching before other executables
Unexpected executable execution chain

XDR Query (Generic)

`Parent process executes child executable repeatedly across multiple binaries`

Splunk (Sysmon)

index=sysmon EventCode=1
| stats count by ParentImage, Image
| where count > 20

5. Registry Persistence (Critical Indicator)

Registry Path

`HKLM\SOFTWARE\Classes\exefile\shell\open\command`

Microsoft Sentinel (KQL)

DeviceRegistryEvents
| where RegistryKey endswith "exefile\\shell\\open\\command"
| project TimeGenerated, DeviceName, RegistryValueData

Severity: Critical
This registry modification forces malware execution before any `.exe`.

6. Windows Defender Tampering Detection

Sentinel KQL

DeviceRegistryEvents
| where RegistryKey contains "Windows Defender"
| where RegistryValueData contains "Disable"

Splunk

`index=wineventlog EventCode=5001 OR EventCode=5007`

7. Obfuscated Binary Execution (ConfuserEx-like)

XDR Indicators

High entropy binaries
Packed executables executing from temp directories

Sentinel KQL

DeviceProcessEvents
| where FolderPath contains "Temp"
| where ProcessCommandLine has_any ("-enc","-decode")

8. Ransomware Encryption Behavior

XDR Behavioral Detection

Rapid file rename activity
Mass file writes in short time window

Sentinel KQL

DeviceFileEvents
| summarize count() by DeviceName, InitiatingProcessFileName, bin(TimeGenerated, 1m)
| where count_ > 500

SOC Response Playbook

Immediately isolate endpoint
Disable compromised accounts
Block attacker IPs
Collect memory & disk images
Restore from offline backups
Rotate credentials